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diff --git a/noao/rv/doc/continpars.hlp b/noao/rv/doc/continpars.hlp
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+.help continpars Jan92 noao.rv
+.ih
+NAME
+continpars -- edit the continuum subtraction parameters
+.ih
+USAGE
+continpars
+.ih
+PARAMETERS
+.ls c_sample = "*"
+Lines or columns to be used in the fits.  The default value ("*") selects
+all pixels.  Type \fIhelp ranges\fR for a complete description of the
+syntax.
+.le
+.ls c_function = "spline3"
+Continuum function to be fit to the image lines or columns.  The functions are
+"legendre" (Legendre polynomial), "chebyshev" (Chebyshev polynomial),
+"spline1" (linear spline), and "spline3" (cubic spline).  The functions
+may be abbreviated.
+.le
+.ls c_interactive = "no"
+Interactively fit the continuum? If set to yes, each spectrum will be fit
+interactively as they are read into the task if the \fIfxcor.continuum\fR
+parameter requires it.  The \fIfxcor\fR keystroke commands 'o' and 't' will
+automatically fit the continuum interactively.
+.le
+.ls naverage = 1
+Number of sample points to combined to create a fitting point.
+A positive value specifies an average and a negative value specifies
+a median.
+.le
+.ls order = 1
+The order of the polynomials or the number of spline pieces.
+.le
+.ls replace = no
+Replace rejected data points with continuum fit points prior to the
+subtraction?  If set to yes, points lying outside the \fIlow_reject\fR or
+\fIhigh_reject\fR limits are replaced by the fit values prior to the 
+continuum subtraction.  This can be useful in removing emission features 
+or cosmic ray events, but great care must be taken in setting other parameters
+in order to get satisfactory results.  Adjusting the \fIgrow\fR or 
+\fIaverage\fR parameters, and using a low order function usually provide
+a good result. 
+.le
+.ls low_reject = 2.,  high_reject = 2.
+Rejection limits below and above the fit in units of the residual sigma.
+.le
+.ls niterate = 1
+Number of rejection iterations.
+.le
+.ls grow = 1.
+When a pixel is rejected, pixels within this distance of the rejected pixel
+are also rejected.
+.le
+
+.ih
+DESCRIPTION
+The \fIcontinpars\fR pset is used to control the continuum subtraction from 
+the data.  When the \fIfxcor\fR task is run in a batch mode, 
+the parameters are used to
+automatically process the data without intervention from the user.  In an
+interactive session, the user may experiment with different parameter values by
+changing them with the allowed colon commands.
+
+Continuum subtraction is done exactly as with the \fIonedspec.continuum\fR
+task.  (Details of the operation are described in the \fIcontinuum\fR 
+documentation.)  The fit to the spectra is subtracted from the data, thus 
+producing a continuum subtracted spectrum suitable for input to the correlation
+routines.  
+
+Users who require the full ability of the \fIonedspec.continuum\fR task to
+supply another form of output spectrum, such as the ratio of the fit, or
+who wish to make use of the "clean" option, should use that task and disable
+continuum subtraction in the \fIrv\fR package tasks.  More functionality is
+planned for this pset in the future.
+
+.ih
+TASK COLON COMMANDS
+The values of the \fIcontinpars\fR pset may be changed, displayed, or updated
+from within tasks that use them by means of various colon commands.  Simply 
+typing the parameter name will have the default action of printing the current
+value of that parameter. 
+.ls :unlearn	continpars
+Reset the continpars pset parameters with their default values.
+The argument "continpars" must be present or else the command will default
+to the \fIfxcor\fR task command.
+.le
+.ls :update	continpars
+Update the continpars pset parameters with the current values.
+The argument "continpars" must be present or else the command will default
+to the \fIfxcor\fR task command.
+.le
+.ls :show	continpars
+Show the current values of the continpars pset parameters.
+The argument "continpars" must be present or else the command will default
+to the \fIfxcor\fR task command.
+.le
+
+The following parameters will be displayed if it's name it typed, and a new 
+value accepted if an argument is given.
+
+.nf
+:c_sample	[range_string]
+:naverage	[int_value]
+:c_function	[spline3|legendre|chebyshev|spline1]
+:order		[int_value]
+:low_reject	[int_value]
+:high_reject	[int_value]
+:niterate	[int_value]
+:grow		[int_value]
+.fi
+
+.ih
+EXAMPLES
+1. List the continuum parameters.
+
+.nf
+	rv> lpar continpars
+.fi
+
+2. Edit the continuum parameters
+
+.nf
+	rv> continpars
+.fi
+.ih
+SEE ALSO
+fxcor, onedspec.continuum, icfit, sfit
+.endhelp
diff --git a/noao/rv/doc/filtpars.hlp b/noao/rv/doc/filtpars.hlp
new file mode 100644
index 00000000..596970ee
--- /dev/null
+++ b/noao/rv/doc/filtpars.hlp
@@ -0,0 +1,167 @@
+.help filtpars Jan91 noao.rv
+.ih
+NAME 
+filtpars -- edit the filter function parameters
+.ih
+USAGE 
+filtpars
+.ih
+PARAMETERS
+.ls f_type = "ramp"
+Type of filter to be used.  Possible choices are
+.ls ramp
+A ramp function which begins to rise at the \fIcuton\fR wavenumber and
+reaches full value (i.e. passes the full value of the component) at the
+\fIfullon\fR wavenumber.  It begin to decline at the \fIcutoff\fR wavenumber
+and returns to zero at the \fIfulloff\fR wavenumber.
+.le
+.ls Hanning
+A Hanning function is used to attenuate the fourier components over the
+range specified by the \fIcuton\fR and \fIcutoff\fR parameters.
+.le
+.ls Welch
+A Welch function is used to attenuate the fourier components over the range
+specified by the \fIcuton\fR and \fIcutoff\fR parameters.
+.le
+.ls Square
+A standard step function which is zero outside the \fIcuton\fR and
+\fIcutoff\fR component numbers and one within those numbers.
+.le
+.le
+.ls cuton = 0
+The fourier wavenumber at which the filter begins to pass the filtered fft
+component.
+.le
+.ls cutoff = 0
+The fourier wavenumber at which the filter ceases to pass fft components.
+.le
+.ls fullon = 0
+Used only for a 'ramp' filter.  The fourier wavenumber at which the filter
+reaches full value and passes all of the data.
+.le
+.ls fulloff = 0
+Used only for a 'ramp' filter.  The fourier wavenumber at which the filter
+reaches zero value and passes none of the data.
+.le
+.ih
+DESCRIPTION 
+The filtering parameters control the type of filter to be used
+on the Fourier transformed data as well as the range in wavenumbers over
+which it will operate.  Filtering of the data may be necessary to remove
+high frequency noise or low-frequency tends not removed by continuum
+subtraction.  If the filtering is enabled, then once the data have been 
+transformed, a bandpass filter of the type chosen by the
+\fIf_type\fR parameter is applied to the Fourier components of the
+spectra.  Wavenumbers lower than that specified by the \fIcuton\fR parameter
+are set to zero and wavenumbers up to that specified by the \fIcutoff\fR
+parameter (or the \fIfulloff\fR parameter in the case of a 'ramp' filter)
+are attenuated or passed in full according to the filter chosen.   
+Since the data are assumed to be linearized in log-wavelength space, applying 
+a filter to the data in Fourier space introduces no phase shift and has 
+the same effect as smoothing the data in real space.  The data are centered 
+and zero padded in an array of length 2**N such that the number of elements 
+is greater than or equal to the number of actual data points.  This array in
+then Fourier transformed, and the resulting fft is then filtered prior
+to correlation.
+
+Filtering is enabled by turning on the \fIfxcor.filter\fR parameter and setting
+it to something other than "none".  Filtering may be done on only one of the
+two spectra or both prior to correlation.
+
+The filter choices behave as follows:
+.ls Square Filter
+The fourier components at wavenumbers between the \fIcuton\fR and \fIcutoff\fR
+wavenumbers are passed without change.  Those wavenumbers outside this region
+are set to zero.
+.le
+.ls Ramp Filter
+Fourier components below the \fIcuton\fR and above the \fIfulloff\fR 
+wavenumbers are set to zero. 
+At the \fIcuton\fR wavenumber the filter function
+begins to rise until the \fIfullon\fR wavenumber is reached.  Data in this 
+region is weighted by the slope of the filter until at the \fIfullon\fR
+wavenumber data are passed through without change.  Similarly, the filter
+begins to fall at the \fIcutoff\fR wavenumber until it completely blocks
+(i.e. zeros) the fourier components at the \fIfulloff\fR wavenumber.
+.le
+.ls Welch Filter
+Fourier components below the \fIcuton\fR and above the \fIcutoff\fR 
+wavenumbers are set to zero.  Components between these regions are weighted
+according to the equation for a Welch window.  Namely,
+.nf 
+
+						     2      
+	w(j)  = 1. - [ (j - 1/2(N-1)) / (1/2(N+1)) ] 
+		        
+		where j =  (wavenumber - cuton_wavenumber) 
+	      	      N =  (cutoff - cuton) + 1
+.fi
+.le
+.ls Hanning Filter
+Fourier components below the \fIcuton\fR and above the \fIcutoff\fR 
+wavenumbers are set to zero. Components between these regions are weighted
+according to the equation for a Hanning window.  Namely,
+.nf
+
+	w(j)  =  1/2 [ 1. - cos( (TWOPI*j) / (N-1) ) ]
+
+		where j =  (wavenumber - cuton_wavenumber) 
+	              N =  (cutoff - cuton) + 1
+.fi
+.le
+
+.ih
+TASK COLON COMMANDS
+The values of the \fIfiltpars\fR pset may be changed, displayed, or updated
+from within the Fourier mode of the \fIfxcor\fR task.  Simply 
+typing the parameter name will have the default action of printing the current
+value of that parameter. An optional value may be added to change the named
+parameter.
+.ls :update  filtpars
+Update the pset with the current values of the filter parameters.
+The argument "filtpars" must be present or else the command will default
+to the task parameters.
+.le
+.ls :unlearn  filtpars
+Reset the parameter values to their defaults.
+The argument "filtpars" must be present or else the command will default
+to the task parameters.
+.le
+.ls :show  filtpars
+Clear the screen and display all values in the filtpars pset.
+The argument "filtpars" must be present or else the command will default
+to the task default.
+.le
+.ls :filttype	[ramp|welch|hanning|square|none]
+Set or show the current value of the filter type to use
+.le
+.ls :cuton	[int_value]
+Set or show the current value of the cuton fourier component
+.le
+.ls :cutoff	[int_value]
+Set or show the current value of the cutoff fourier component
+.le
+.ls :fullon	[int_value]
+Set or show the current value of the fullon fourier component
+.le
+.ls :fulloff	[int_value]
+Set or show the current value of the fulloff fourier component
+.le
+
+.ih
+EXAMPLES
+1. List the filtering parameters.
+
+.nf
+	rv> lpar filtpars
+.fi
+
+2. Edit the filtering parameters
+
+.nf
+	rv> filtpars
+.fi
+.ih
+SEE ALSO
+fxcor
+.endhelp
diff --git a/noao/rv/doc/fxcor.hlp b/noao/rv/doc/fxcor.hlp
new file mode 100644
index 00000000..7f253a3b
--- /dev/null
+++ b/noao/rv/doc/fxcor.hlp
@@ -0,0 +1,1143 @@
+.help fxcor Mar93 noao.rv
+.ih
+NAME
+fxcor -- compute radial velocities via Fourier cross correlation
+.ih
+USAGE
+fxcor objects templates
+.ih
+PARAMETERS
+.ce
+INPUT PARAMETERS
+.ls objects
+The list of image names for the input object spectra.
+.le
+.ls templates
+The list of image names that will be used as templates for the cross
+correlation.  This list need not match the object list.  All pairs
+between the two lists will be correlated.
+.le
+.ls apertures = "*"
+List of apertures to be correlated in echelle and multispec format spectra.  
+This parameter is used for \fIboth\fR the object and reference spectra if both
+spectra are two dimensional, otherwise the aperture list applies to the object
+only if the template is one-dimensional.  Individual apertures from a
+two-dimensional template may be
+extracted to 1-D using the \fIonedspec.scopy\fR task, and these new images may
+then be used in the template list as separate images.  (See the examples for
+how this may be done). The default of '*' means to process all of the
+apertures in the spectrum.  Note that the sample regions named by the 
+\fIosample\fR and \fIrsample\fR parameters will apply to all apertures.
+.le
+.ls cursor = ""
+Graphics cursor input.
+.le
+
+.ce
+DATA PREPARATION PARAMETERS
+.ls continuum = "both"
+Continuum subtract the spectra prior to correlation?  Possible values for
+this parameter are any of the strings (or abbreviations) "object" (for object 
+spectrum only), "template" (for template spectrum only), "both" for 
+continuum flattening both object and template spectra, or "none" for 
+flattening neither spectrum.  The \fIcontinpars\fR pset is used to specify 
+the continuum fitting parameters.
+.le
+.ls filter = "none"
+Fourier filter the spectra prior to correlation?  Possible values for
+this parameter are any of the strings (or abbreviations) "object" (for object 
+spectrum only), "template" (for template spectrum only), "both" for 
+fourier filtering both object and template spectra, or "none" for 
+filtering neither spectrum.  The \fIfiltpars\fR pset holds the parameters 
+for the filtering (filter type and width).
+.le
+.ls rebin = "smallest"
+Rebin to which spectrum dispersion?  If the input dispersions are not equal
+prior to the correlation,
+one of the two spectra in the pair will be rebinned according to the
+\fIrebin\fR parameter.  Possible values are "smallest" (to rebin to the
+smaller of the two values), "largest" (to rebin to the larger of the two
+values), "object" (to force the template to always be rebinned to the object
+dispersion), and "template" (to force the object to always be rebinned to the
+template dispersion).  Input spectra \fImust be\fR linearly corrected.
+Support for non-linear input dispersions is not included in this release.
+.le
+.ls pixcorr = "no"
+Do a pixel-only correlation, ignoring any dispersion information?  If this
+parameter is set to \fIyes\fR, then regardless of whether dispersion
+information is present in the image headers, the correlation will be done
+without rebinning the data to a log-linear dispersion.  This option is useful
+when pixel shifts, not velocities, are the desired output.
+.le
+.ls osample = "*"
+Sample regions of the object spectrum to be used in the correlation specified
+in pixels if the first character is a 'p', or angstroms if the first
+character is an 'a'.  The default (i.e. no 'a' or 'p' as the first
+character) if a range is provided, is a range specified in angstroms.
+This string value will be updated in an interactive session as sample
+regions are re-selected in spectrum mode. The default, '*', is the entire 
+spectrum.  The region is specified as a starting value, a '-', and an ending 
+value.  If the specified range is out of bounds, the endpoints will be 
+modified to the nearest boundary, or else the entire spectrum will be 
+correlated if the whole range is out of bounds.
+.le
+.ls rsample = "*"
+Sample regions of the template spectrum to be used in the correlation specified
+in pixels if the first character is a 'p', or angstroms if the first
+character is an 'a'.  The default (i.e. no 'a' or 'p' as the first
+character) if a range is provided, is a range specified in angstroms.
+This string value will be updated in an interactive session as sample
+regions are re-selected in spectrum mode. The default, '*', is the entire 
+spectrum.  The region is specified as a starting value, a '-', and an ending 
+value.  If the specified range is out of bounds, the endpoints will be 
+modified to the nearest boundary, or else the entire spectrum will be 
+correlated if the whole range is out of bounds.
+.le
+.ls apodize = 0.2
+Fraction of endpoints to apodize with a cosine bell when preparing the data
+prior to the FFT.
+.le
+
+.ce
+CORRELATION PEAK FITTING PARAMETERS
+.ls function = "gaussian"
+Function used to find the center and width of the correlation peak.
+Possible choices are "gaussian", "parabola", "lorentzian", "center1d",
+or "sinc".  If a center1d fit is selected, then only the center is determined.
+A "sinc" function uses a sinc interpolator to find the maximum of the 
+peak by interpolating the points selectes.  The FWHM calculation in this
+case is computed empirically by finding the half power point according
+to the computed peak height and the \fIbackground\fR level.  No FWHM 
+will be computed of the background is not set.  The function fitting options
+all compute the FWHM from the fitted coefficients of the function.
+.le
+.ls width = INDEF
+Width of the fitting region in pixels.  The fitting weights are
+zero at the endpoints so the width should be something
+like the expected full width.  If INDEF, then the width is
+set by the \fIheight\fR and \fIpeak\fR parameters. If other than INDEF, 
+this parameter will override the \fIheight\fR and \fIpeak\fR parameters.
+.le
+.ls height = 0.
+The width of the fitting region is defined by where the correlation
+function crosses this height starting from the peak.  The height is
+specified as either a normalized correlation level (this is like
+the 'y' interactive key) or normalized to the peak.  The type of
+level is selected by the \fIpeak\fR parameter.
+.le
+.ls peak = no
+Measure the height parameter relative to the correlation peak value
+rather than as a normalized correlation level? If yes, then \fIheight\fR
+is a fraction of the peak height with an assumed base of zero.
+.le
+.ls minwidth = 3., maxwidth = 21.
+The minimum and maximum widths allowed when the width is determined
+from the height.
+.le
+.ls weights = 1.
+Power of distance defining the fitting weights.  The points used
+in fitting the correlation peak are weighted by a power of the
+distance from the center as given by the equation
+.nf
+
+         weight = 1 - (distance / (width/2)) ** \fIweights\fR
+
+.fi
+Note that a weight parameter of zero is equivalent to uniform weights.
+The center1d fitting algorithm uses it's own weighting function.
+.le
+.ls background = 0.0
+Background level, in normalized correlation units, for a Gaussian or 
+Lorentzian fitting function.  If set to INDEF, the background is a free 
+parameter in the fit.
+.le
+.ls window = INDEF
+Size of the window in the correlation plot.  The peak will be displayed
+with a window centered on the peak maximum and two times \fIwindow\fR 
+pixels wide if no dispersion information is present in the image header.
+If dispersion information is present, \fIwindow\fR is specified in Km/s.
+A value of INDEF results in a default window size of 20 pixels.  If the
+window proves to be too small for the number of points to be fit selected 
+with the \fIwidth\fR, \fIheight\fR, and/or \fIpeak\fR parameters, a message
+will be written to the ".log" file and/or screen explaining that points
+outside the window bounds were used in the fit.  The user may wish to
+review this fit or increase the window size.
+.le
+.ls wincenter = INDEF
+Center of the peak search window specified in pixel lags if no dispersion
+information is present, or specified in Km/s if dispersion information is
+present.  If set to the default INDEF, the maximum peak in the cross-correlation
+function will be fit by default.  If set to other than INDEF, the maximum peak 
+within a window centered on \fIwincenter\fR and two times \fIwindow\fR 
+lags wide will be used.  Note that this parameter can be used to constrain
+the velocities computed to a certain range in non-interactive mode.
+.le
+
+.ce
+OUTPUT PARAMETERS
+.ls output = ""
+Name of the file to which output will be written.  If no file name is given
+then no log files will be kept, but the user will be queried for a file name
+if a write operation is performed.  Tabular text output will have a ".txt" 
+suffix appended to the \fIoutput\fR name, a verbose description of each fit
+will have ".log" suffix appended and will be written only if the \fIverbose\fR
+parameter is set, and the graphics metacode file will be appended with 
+a ".gki" suffix. (NOTE: Image names will be truncated to 10 characters in the
+output file because of space considerations.  Verbose output logs will
+truncate the image names to 24 characters.  Object names are similarly
+truncated to 15 characters.  If a relative velocity is calculated with a
+redshift of more than 0.2, output will be redshift z values rather than
+velocities in Km/s.)
+.le
+.ls verbose = "long"
+Set level of verbosity and types of files to create.  The \fIverbose\fR
+parameter is an enumerated string whose values determine the number and type
+of output files created.  Up to three files are created: the ".txt", ".log",
+and ".gki" files (see the description for the \fIoutput\fR parameter).
+Possible values  for \fIverbose\fR and the files created are as follows:
+.nf
+
+    Value:      Files Created:
+
+    short       (an 80-char .txt file and a .gki file)
+    long        (a 125-char .txt file, a .log file, a .gki file)
+    nolog       (a 125-char .txt file and a .gki file)
+    nogki       (a 125-char .txt file and a .log file)
+    txtonly     (a 125-char .txt file)
+    stxtonly    (an 80-char .txt file)
+
+.fi
+The \fIfields\fR task 
+may be used to strip out selected columns from the .txt files.  The 125-char
+.txt output
+may be printed without wrapping the lines either in landscape mode for
+a laser printer, or on a 132 column lineprinter.
+.le
+.ls imupdate = "no"
+Update the image header with the computed velocities?  If set to yes, then
+the image will be updated with the observed and heliocentric velocities
+by adding the \fIkeywpars.vobs\fR and \fIkeywpars.vhelio\fR keywords
+respectively.  Two-dimensional spectra cannot be updated.  Additional keywords
+defined in the \fIkeywpars\fR pset will also be updated.
+.le
+.ls graphics = "stdgraph"
+Output graphics device.
+.le
+
+.ce
+CONTROL PARAMETERS
+.ls interactive = "yes"
+Process the spectra interactively?  
+.le
+.ls autowrite = "yes"
+Automatically record the last fit to the log file when moving to the 
+next/previous spectrum or quitting? If set to "no", the user will be 
+queried whether to write the results if no write was performed, and 
+possibly queried for a file name if \fIoutput\fR isn't set.  
+.le
+.ls autodraw = "yes"
+Automatically redraw the new fit after it changes.  If set to the default
+"yes" then the old fit is erased and a new one computed and drawn after 
+the 'g', 'y', 'd', or 'b' keystrokes.  If set to "no", then old fits are not
+erased and the user must redraw the screen with an 'r' keystroke.
+.le
+.ls ccftype = "image"
+Type of output to create when writing out the correlation function with
+the ":wccf file" command.  Possible choices are "text" which will be a
+simple list of (lag,correlation_value) pairs, or "image" which will be an
+IRAF image whose header would describe the lag limits and selected peak.
+.le
+
+.ce
+ADDITIONAL PARAMETER SETS
+.ls observatory = "kpno"
+The location of the observations, as defined by the \fInoao.observatory\fR
+task.  The image header keyword OBSERVAT will override this parameter, thus
+allowing for images which were taken at another observatory to be properly
+corrected.  These values are used in the heliocentric correction routines.
+.le
+.ls continpars = ""
+The continuum subtraction parameters as described in the \fIcontinpars\fR 
+named pset.
+.le
+.ls filtpars = ""
+The parameter set defining the parameters to be used in filtering the
+data prior to the correlation. 
+.le
+.ls keywpars = ""
+The image header keyword translation table as described in 
+the \fIkeywpars\fR named pset.
+.le
+
+.ce
+RV PACKAGE PARAMETERS
+.ls dispaxis = 1,  nsum = 1
+Parameters for defining vectors in 2D images.  The
+dispersion axis is 1 for line vectors and 2 for column vectors.
+A DISPAXIS parameter in the image header has precedence over the
+\fIdispaxis\fR parameter. 
+.le
+.ls z_threshold = 0.2
+Redshift value at which the output logs switch from printing velocities in 
+units of Km/s to redshift z values.
+.le
+.ls tolerance = 1.0e-5
+Fitting tolerance for Least Squares fitting.
+.le
+.ls maxiters = 100
+Maximum number of iterations for Least Squares fitting or any other iterative
+algorithm.
+.le
+.ls interp = "poly5"
+Interpolator used when rebinning the data to a log-linear dispersion.   See 
+the section on interpolation for more information.  Possible choices are
+"nearest", "linear", "poly3", "poly5", "spline3", and "sinc".
+.le
+.ls line_color = 1
+Color index of overlay plotting vectors.  This parameter has no effect on
+devices which do not support color vectors.
+.le
+.ls text_color = 1
+Color index of plot text annotation.  This parameter has no effect on
+devices which do not support color vectors.
+.le
+.ls observatory = "observatory"
+Observatory at which the spectra were obtained if not specified in the
+image header by the keyword OBSERVAT.  This parameter is used by several
+tasks in the package through parameter redirection so this parameter may be
+used to affect all these tasks at the same time.  The observatory may be
+one of the observatories in the observatory database, "observatory" to
+select the observatory defined by the environment variable "observatory" or
+the parameter \fBobservatory.observatory\fR, or "obspars" to select the
+current parameters set in the \fBobservatory\fR task.  See help for
+\fBobservatory\fR for additional information.
+.le
+
+.ih
+DESCRIPTION
+\fIFxcor\fR performs a Fourier cross-correlation on the input list of object
+and template spectra.  Object spectra may be either one or two dimensional
+(in `echelle' or `multispec' format), and may be correlated against a one
+or two dimensional template.  If the template spectrum is only one dimensional
+but the object is two dimensional, the template is used to correlate each of
+the apertures specified by the \fIapertures\fR parameter in the object 
+spectrum.  Two dimensional templates will correlate corresponding apertures.
+
+If the input spectra are not dispersion corrected (DC-FLAG parameter missing
+or less than zero), or the \fIpixcorr\fR parameter is turned on, then only 
+a pixel space correlation is done.  This is
+appropriate for a simple cross-correlation of images whether spectra or not.
+If the spectra are dispersion corrected, a log binned correlation is
+performed and various radial velocity measurements are made. At a minimum,
+a relative velocity between the object and template spectra is produced.
+If the image headers contain sufficient information for heliocentric
+velocity corrections (see help for \fBkeywpars\fR), the corrections are
+computed and possibly recorded in the image header (see below for a full
+explanation of the computed velocities).  If the value of the 
+heliocentric velocity is returned as INDEF, the user may use the 'v'
+keystroke to see the full results of the correlation, including errors
+which occured causing the corrections to not be done.
+
+A number of operations may be performed to prepare the data for
+correlation.  If a linear wavelength dispersion is defined, the spectra are
+rebinned to a log-linear dispersion using the interpolant set by the package
+parameter \fIinterp\fR (See the section on interpolation for details).  
+At this time only linear input dispersions are supported for rebinning.
+The starting and ending wavelength for
+both spectra will remain the same, but the dispersion in log space will be
+determined from the \fIrebin\fR parameter if the input disersions aren't
+equal, or from the spectrum's endpoints and number of pixels if they are
+equal.  For example, assuming \fIrebin\fR is set to "smallest", if object
+one and the template have the same input log dispersion of 0.5e-4 A/pix the
+data will not be rebinned.  Object two with a wpc of 0.4e-4 A/pix will force
+the template to be rebinned to a common wpc of 0.4e-4 A/pix.  If the third
+object on the list then has a dispersion of 0.3e-4 A/pix, the template will
+again be rebinned from the original 0.5e-4 A/pix dispersion to a new 0.3e-4
+A/pix dispersion.  If object three and the template are the same star, the
+template spectrum will suffer from interpolation errors that should be
+considered when analyzing the results.  The output .txt file will update
+every time the common dispersion is changed.  The suggested course of action
+is to bin all spectra to the same dispersion, preferably a log-linear one,
+prior to executing this package.
+
+If the \fIcontinuum\fR flag is set to something other than 
+"none", the object and/or template data will
+be continuum subtracted using the fitting parameters found in the
+\fIcontinpars\fR pset on input.  The data are zeroed outside the sample
+region specified by the \fIosample\fR and \fIrsample\fR parameters, 
+the ends of each region are apodized, and the bias is then subtracted.
+If the \fIfilter\fR flag is set to something other than
+"none", the data are Fourier filtered according to the parameters in 
+the \fIfiltpars\fR pset prior to the correlation computation.
+
+Once the correlation is computed, the maximum peak within the window
+specified by the \fIwincenter\fR and \fIwindow\fR parameters is found and
+fit according to the \fIwidth\fR or \fIheight\fR and \fIpeak\fR parameters.
+A small, unlabeled plot of the entire cross correlation function (hereafter
+CCF) is drawn above a larger, expanded plot centered on the peak in a window
+of size specified by the \fIwindow\fR parameter.  The dashed lines in the
+small plot show the limits of the expanded plot.  The bottom axis of the
+expanded plot is labeled with pixel lag and, if dispersion information is
+present, the top axis is labeled with relative velocity.  To choose a
+different peak to fit, move the cursor to the top plot of the whole ccf and
+hit the 'z' keystroke at the desired peak.  The plot will be redrawn with
+the new peak now centered in the window and a fit automatically done.  The
+status line will contain a summary of the pixel shift from the fit and
+optional velocity information.  The 'v' keystroke may be used to suspend
+graphics and get a more detailed description of the correlation and fit, and
+the '+' keystroke will toggle the status line output.  To view the
+antisymmetric noise component of the correlation function, simply hit the
+'a' keystroke followed by any keystroke to return to the correlation plot.
+Similarly, the 'e' keystroke may be used to preview the summary plot of the
+correlation, again hitting any key to return to the correlation.  An
+overplot of the subtracted fit (residuals) may be seen with the 'j'
+keystroke.
+
+If the user is dissatisfied with the fit to the peak, he can mark the left
+and right side of the peak with the 'g' keystroke to redo the fit, or else
+set the cursor to mark a cutoff with the 'y' keystroke, and all points from
+the peak maximum to the cursor will be fit.  To fix the background of a
+Gaussian fit (i.e. change the \fIbackground\fR parameter graphically), type
+the 'b' keystroke at the desired level, and a new fit will be done.  The 'r'
+keystroke may be used at any time to redraw the plot, and the 'x' keystroke
+can be used to compute a new correlation if any of the parameters relating
+to the correlation are changed (e.g. the apodize percentage).  New
+correlations are automatically computed when new images are read in, the
+data are continuum subtracted, a different region is selected for
+correlation, or Fourier filtering is done.  Certain colon commands from
+within the Fourier or Spectrum mode will also cause a new correlation to be
+computed when these modes are exited.
+
+The 'c' keystroke may be used to get a printout of the cursor position in both 
+lag and relative velocity.  The cursor may be positioned in either the
+unlabeled CCF plot on the top, or in the zoomed plot on the bottom.  This is
+useful for judging the FWHM calculation, or estimating the velocity of a
+peak without using the 'z' keystroke to zoom and fit.  Note that because of
+the plotting implementation, the normal cursor mode keystroke \fIshift-C\fR
+should not be used as it may return erroneous results depending upon cursor
+position.  Note also that velocities printed are only approximate relative
+velocities, and the user should properly fit a peak or use the ":correction"
+command to get a true heliocentric velocity.
+
+For binary star work, the user may type the 'd' and/or '-' keystrokes to fit
+and then subtract up to four Gaussians to the peaks. See the discussion
+below for more deatils on the use of this feature.  If multiple peaks were
+fit, a separate entry will be made in the log file for each peak with a
+comment that it was part of a blended peak.  The metacode file will contain
+only one summary plot with each peak marked with it's heliocentric velocity
+or pixel shift.
+
+To move to the next spectrum in a list (of images or apertures), simply hit
+the 'n' keystroke.  Similary, the 'p' keystroke will move to the previous
+spectrum.  These commands have a hitch, though.  By default, the
+next/previous commands will move first to the next template in the template
+image list.  Once the end of the template image list is reached, the next
+spectrum will be the next aperture in the list specified by \fIapertures\fR,
+resetting the template image list automatically and possibly updating the
+aperture in the template image as well.  Finally, after correlating all of
+the templates against all of the apertures, the next/previous command will
+move to the next object image, again resetting the template image and/or
+aperture list.  To override this sequence, the user may use the ":next" or
+":previous" commands and specify one of "aperture", "object", or
+"template".  If \fIautowrite\fR is set, the results of the last fit will be
+written to the log automatically.  To write any one of the fits explicitly,
+use the 'w' keystroke.
+
+The \fIfxcor\fR task also contains three submodes discussed in detail below.
+Briefly, the 'f' keystroke will put the user in the "fourier mode",
+where he can examine the Fourier transform of the spectra in various
+ways and change/examine the filtering parameters.  The 'o' and 't'
+keystrokes let the user examine and fit the continuum for the object
+and template spectra, respectively, using the \fBicfit\fR commands.
+Upon exiting the continuum fitting the spectra are continuum subtracted 
+and a new correlation is computed.  Finally the 's' keystroke will put
+the user in "spectrum mode", in which he may graphically select the
+region to be correlated, compute an approximate shift using the cursor,
+or simply examine the two spectra in a variety of ways.  All of these
+submodes are exited with the 'q' keystroke, after which the correlation
+will be redone, if necessary, and the CCF plot redrawn.
+
+Colon commands may also be used to examine or change parameter values in
+any of the \fIfiltpars\fR, \fIcontinpars\fR, or \fIkeywpars\fR
+psets.  Simply type a ':' followed by the parameter name and an optional
+new value.  The \fIobservatory\fR parameters may only be changed outside
+the task.
+
+To exit the task, type 'q'.  Results will be saved
+to the logfile automatically if one was specified, otherwise the user will
+be asked if he wants to save the results, and if so, queried for a file name
+before exiting if no \fIoutput\fR file was defined.
+
+If the \fIoutput\fR parameter is set, several files will be created
+depending on the value of the \fIverbose\fR parameter (see the parameter
+description for details).  These include a file with a ".gki" suffix
+containing metacode output of a summary plot, a ".txt" suffix file
+containing text output in the standard IRAF 'list' format containing either
+verbose or non-verbose output, and a third file having a ".log" suffix
+containing a verbose description of the correlation and fit, as well as any
+warning messages.  This contents of the ".log" file is identical to what is
+seen with the 'v' keystroke.  If the computed relative velocity exceeds the
+package parameter \fIz_threshold\fR, the ".txt" file will contain redshift Z
+values rather than the default velocities.  Text file output may be have
+selected columns extracted using the iraf \fIfields\fR task (where string
+valued fields will have blank spaces replaced with an underscore), and
+specific metacode plots may be extracted or displayed with the iraf
+\fIgkiextract\fR and/or \fIstdgraph\fR/\fIgkimosaic\fR tasks.
+
+(References: Tonry, J. and Davis, M. 1979 \fIAstron. J.\fR \fB84,\fR 1511, 
+and Wyatt, W.F. 1985 in \fIIAU Coll. No 88, Stellar Radial Velocities\fR, 
+p 123).
+
+.ih
+FOURIER MODE DESCRIPTION
+Fourier mode is entered from the main task mode via the 'f' keystroke.  By 
+default, the user is presented with a split plot of the power spectra of
+the object and template spectra (object on top) and the requested filter
+overlayed. The X-axis is double-labeled with wavenumbers on the bottom of
+the screen and frequency on top.  The ":log_scale" command can be used to 
+toggle the log scaling of the Y-axis of the plot, and the ":overlay" command 
+will toggle whether or not the filter function (if specified) is overlayed 
+on the plot.  By default the entire power spectrum is displayed, but 
+the ":zoom" command may be used to specify a blowup factor for the 
+display (e.g. ":zoom 2" will display only the first half of the power 
+spectrum).  Plot scaling and content parameters are learned for the next 
+invocation of this mode.
+
+The plot contents may also be changed through various keystroke commands.
+The 'p' keystroke will display the power spectrum (the default) and the 'f'
+keystroke will display the two FFT's.   The 'b' and 'g' 
+keystrokes may be used to examine the power spectra and FFT's 
+respectively \fIbefore\fR filtering.  The user can determine the period 
+trend in the data by placing the cursor at a particular wavenumber/frequency 
+and hitting the 'i' keystroke (this command will not work on a plot of 
+the filtered spectra).  The 'r' key will redraw whichever plot is currently
+selected and a 'q' will return the user to the mode which called the Fourier
+mode (i.e. either the main task mode or the Spectrum mode).  The Spectrum
+mode may be entered from within Fourier mode via the 's' keystroke.
+
+Colon commands are also used to specify or examine the filtering parameters
+by simply typing a ':' followed by the parameter name found in 
+the \fIfiltpars\fR pset.
+
+.ih
+CONTINUUM MODE DESCRIPTION
+Automatic continuum subtraction is controlled by the \fIcontinpars\fR
+pset.  These may be reset from the main
+correlation function mode.  To interactively fit and modify the continuum
+fitting parameters the 'o' and 't' keys are used.  This enters
+the ICFIT package which is described elsewhere (see \fIicfit\fR).  
+Exiting the fitting,
+with 'q', causes a recomputation of the correlation function and peak
+fit.  To view the flattened spectra use the spectrum review mode
+entered with the 's' key.  Fitting parameters changed while doing the
+interactive continuum fitting are learned.
+
+.ih
+SPECTRUM MODE DESCRIPTION
+Spectrum mode is entered from the main or fourier mode via the 's'
+keystroke.  The user may select plots of the original input spectra with the
+'i' keystroke, or the continuum subtracted spectra with the 'n' keystroke,
+If the data have been rebinned to a log scale, they will still be plotted 
+on a linear wavelength scale for clarity.  Pixel data are plotted identically
+to how they were read.  (NOTE: For rebinned spectra, a slight slope may be
+noticed in the 'original' data because of rebinning effects.)
+In addition, a sample regions (if selected) for the correlation are marked
+on the bottom of both plots.  To select a new sample region, use the 's'
+keystroke to select the endpoints of the region.  An 's' keystroke on the
+top plot will select a sample region for the object spectrum, and an 's' on
+the bottom plot will select a template sample, using the 'b' keystroke will
+select both samples simultaneously.  The regions may be selected
+explicitly by using the ":osample" and ":rsample" commands, and selected
+sample regions may be cleared entirely using the (e.g.) ":osample *" command,
+or individual regions may be unselected by putting the cursor within the
+region and typing 'u'.  See the
+parameter description for syntax of the sample ranges.  Regions will be
+checked and possibly truncated to see if they 
+lie within the range of the spectrum.  The 'd'
+keystroke may be used to print the difference in pixels (and/or velocity)
+between two points on the spectrum.  This is useful for getting an
+approximate shift.  Fourier mode may be entered via the 'f' keystroke.  To
+return to the correlation simply type 'q' or 'x'.
+
+In addition to the above commands, the user may examine or change the 
+parameters in the \fIcontinpars\fR pset by simply typing a ':' followed
+by the parameter name. Changing these values will not cause a new correlation
+until an explicit command is given to redo the continuum subtraction.
+
+(NOTE: More functionality is planned for this mode.)
+
+.ih
+INTERPOLATION
+The interpolation type is set by the package parameter \fIinterp\fR.
+The available interpolation types are:
+
+.nf
+	nearest - nearest neighbor
+	 linear - linear
+	  poly3 - 3rd order polynomial
+	  poly5 - 5th order polynomial
+	spline3 - cubic spline
+	   sinc - sinc function
+.fi
+
+The default interpolation type is a 5th order polynomial (poly5).
+
+The choice of interpolation type depends on the type of data, smooth
+verses strong, sharp, undersampled features, and the requirements of
+the user.  The "nearest" and "linear" interpolation are somewhat
+crude and simple but they avoid "ringing" near sharp features.  The
+polynomial interpolations are smoother but have noticible ringing
+near sharp features.  They are, unlike the sinc function described
+below, localized.
+
+In V2.10 a "sinc" interpolation option is available.  This function
+has advantages and disadvantages.  It is important to realize that
+there are disadvantages!  Sinc interpolation approximates applying a phase
+shift to the fourier transform of the spectrum.  Thus, repeated
+interpolations do not accumulate errors (or nearly so) and, in particular,
+a forward and reverse interpolation will recover the original spectrum
+much more closely than other interpolation types.  However, for
+undersampled, strong features, such as cosmic rays or narrow emission or
+absorption lines, the ringing can be more severe than the polynomial
+interpolations.  The ringing is especially a concern because it extends
+a long way from the feature causing the ringing; 30 pixels with the
+truncated algorithm used.  Note that it is not the truncation of the
+interpolation function which is at fault!
+
+Because of the problems seen with sinc interpolation it should be used with
+care.  Specifically, if there are no undersampled, narrow features it is a
+good choice but when there are such features the contamination of the
+spectrum by ringing is much more severe than with other interpolation
+types.
+
+.ih
+DEBLENDING
+When entering the deblending function, two cursor settings define the
+local background, which may be sloping, and the region to be fit.  Note
+that both the x and y of the cursor position are used.  The lines to be
+fit are then entered either with the cursor ('m'), or by typing the
+shifts ('t').  The latter is useful if the shifts of the
+lines are known accurately and if fits restricting the absolute or
+relative positions of the lines will be used (i.e. 'a', 'b', 'd',
+'e').  A maximum of four lines may be fit.  If fewer lines are desired,
+exit the marking step with 'q'.
+
+There are six types of fits which may be selected.  This covers all
+combinations of fixing the absolute positions, the relative positions,
+the sigmas to be the same, and letting all parameters be determined.
+In all cases the peak intensities are also determined for each line.
+The options are given below with the appropriate key and mnemonic.
+
+.nf
+    a=0p1s	Fit intensities and one sigma with positions fixed
+    b=1p1s	Fit intensities, one position, and one sigma with
+			separations fixed
+    c=np1s	Fit intensities, positions, and one sigma
+    d=0pns	Fit intensities and sigmas with positions fixed
+    e=1pns	Fit intensities, one position, and sigmas with
+			separations fixed
+    f=npns	Fit intensities, positions, and sigmas
+.fi
+
+This list may also be printed with the '?' key when in the deblending
+function.
+
+As noted above, sometimes the absolute or relative shifts of the
+lines are known a priori and this information may be entered by typing
+the shifts explicitly using the 't' option during marking.  In
+this case, one should not use the 'c' or 'f' fitting options since they
+will adjust the line positions to improve the fit.  Options 'a' and 'd'
+will not change the lines positions and fit for one or more sigmas.
+Options 'b' and 'e' will maintain the relative positions of the lines
+but allow an other than expected shift.
+
+After the fit, the modeled lines are overplotted.  The line center,
+flux, equivalent width, and full width half maximum are printed on the
+status line for the first line.  The values for the other lines and
+the RMS of the fit may be examined by scrolling the status line
+using the '+', '-', and 'r' keys.  Velocity information is obtained by
+typing the 'v' keystroke.  To continue enter 'q'.
+
+The fitting may be repeated with different options until exiting with 'q'.
+
+The fitted model may be subtracted from the data (after exiting the
+deblending function) using the '-' (minus)
+keystroke to delimit the region for which the subtraction is to
+be performed. This allows you to fit a portion of a peak which may
+be contaminated by a blend and then subtract away the entire peak
+to examine the remaining components.
+
+The fitting uses an interactive algorithm based on the Levenberg-Marquardt
+method.  The iterations attempt to improve the fit by varying the parameters
+along the gradient of improvement in the chi square.  This method requires
+that the initial values for the parameters be close enough that the
+gradient leads to the correct solution rather than an incorrect local
+minimum in the chi square.  The initial values are determined as follows:
+
+.nf
+    1.  The initial line centers are those specified by the user
+	either by marking with the cursor or entering the shifts.
+    2.  The initial peak intensities are the data values at the
+	given line centers with the marked continuum subtracted.
+    3.  The initial sigmas are obtained by dividing the width of
+	the marked fitting region by the number of lines and then
+	dividing this width by 4.
+.fi
+
+Note that each time a new fitting options is specified the initial parameters
+are reset.  Thus the results do not depend on the history of previous fits.
+However, within each option an iteration of parameters is performed as
+described next.
+
+The iteration is more likely to fail if one initially attempts to fit too
+many parameters simultaneously.  A constrained approach to the solution
+is obtained by iterating starting with a few parameters and then adding
+more parameters as the solution approaches the true chi square minimum.
+This is done by using the solutions from the more constrained options
+as the starting point for the less constrained options.  In particular,
+the following iterative constraints are used during each option:
+
+.nf
+	a: 0p1s
+	b: 0p1s, 1p1s
+	c: 0p1s, 1p1s, np1s
+	d: 0p1s, 0pns
+	e: 0p1s, 1p1s, 1pns
+	f: 0p1s, 1p1s, np1s, npns
+.fi
+
+For example, the most general fit, 'f', first fits for only a single sigma
+and the peak intensities, then allows the lines to shift but keeping the
+relative separations fixed. Next, the positions are allowed to vary
+independently but still using a single sigma, and then allows all parameters
+to vary.
+
+To conclude, here are some general comments.  The most restrictive 'a'
+key will give odd results if the initial positions are not close to the
+true centers.  The most general 'f' can also lead to incorrect results
+by using unphysically different sigmas to make one line very narrow and
+another very broad in an attempt to fit very blended lines.  The
+algorithm works well when the lines are not severely blended and the
+shapes of the lines are close to Gaussian.
+
+.ih
+PEAK FITTING/FINDING ALGORITHMS
+Determining the center of the cross correlation peak is the key step in
+measuring a relative shift or velocity between the object and template.
+The width of the correlation peak is also of interest for measuring
+a line broadening between the two samples.  Since people have different
+preferences and prejudices about these important measurements, a variety
+of methods with a range of parameters is provided.
+
+In all cases, one must specify the fitting function and a sample width; i.e.
+the range of points about the correlation peak to be used in the
+measurement.  Note that the width defines where the fitting weights vanish
+and should be something like the full width.  For the CENTER1D algorithm the
+maximum weights are at the half width points while for the other methods
+(with the exception of "sinc") greater weight is given to data nearer the
+center.
+
+The width may be specified in three ways.  The first is as an actual
+width in pixels.  This is the most straightforward and is independent
+of quirks in the actual shape of the peak.  The second way is to find
+where the correlation function crosses a specified height or level.
+The height may be specified in normalized correlation units or as a
+fraction of the peak height.  The former is equivalent to the
+interactive 'y' key setting while the latter may be used to select some
+"flux" point.  A value of 0.5 in the latter would be approximately the
+full width at half intensity point except that the true zero or base of
+the peak is somewhat uncertain and one needs to keep in mind that the
+weights go to zero at this point.  Note that a level may be negative.
+In this method the actual width may go to zero or include the entire
+data range if the level fall above the peak or below the minimum of the
+correlation.  The minimum and maximum width parameters are applied to
+constrain the fitting region.  The last method is to interactively mark
+the fitting region with the 'g' key.
+
+There are five methods for determining the correlation peak position.  The
+CENTER1D algorithm has been heavily used in IRAF and is quite stable and
+reliable.  It is independent of a particular model for the shape of the peak
+or the background determination and is based on bisecting the integral.  It
+uses antisymmetric weights with maxima at points half way between the
+estimated center and the fitting region endpoint.  A parabola fit and sinc
+interpolation is also independent of background determinations.  The
+parabola is included because it is a common method of peak centering.
+
+The sinc option uses a sinc interpolator together with a maximization
+(actually a minimization algorithm) function to determine the peak height
+and center.  A width will be computed only if a background level has been
+set and is determined empirically based on the peak height and background.
+Point weighting is not used in this option.
+
+The gaussian and lorentzian function fits are model dependent and
+determine a center, width, and peak value.  The background may also
+be determined simultaneously but this extra degree of freedom
+for a function which is not strictly gaussian or lorentzian may
+produce results which are sensitive to details of the shape of the
+correlation function.  The widths reported are the full width at
+half maximum from the fits.
+
+The parabola, gaussian, and lorentzian methods use weights which
+vary continuously from 1 at the estimated center to zero at the
+endpoints of the fitting region.  The functional form of the
+weights is a power law with specified exponent.  A value of zero
+for the exponent produces uniform weights.  However, this is
+discontinuous at the endpoints and so is very sensitive to the data
+window.  A value of one (the default) produces linearly decreasing weights.
+
+All these methods produce centers which depend on the actual
+data points and weights used.  Thus, it is important to iterate
+using the last determined center as the center of the data window
+with continuous weights in order to find a self-consistent center.
+The methods are iterated until the center does not change by more
+than 0.01 pixels or a maximum of 100 iterations is reached.
+
+Errors in the pixel shift are computed from the center parameter of the fitting
+function.  Velocity errors are computed based on the fitted peak height and
+the antisymmetric noise as described in the Tonry & Davis paper (1979,
+\fIAstron. J.\fR \fB84,\fR 1511). Dispersion/pixel-width errors are 
+not computed in this release but are planned for a future release.
+
+The initial peak fit will be the maximum of the CCF.  This will be the only 
+peak fit in non-interactive mode but a confidence level will be entered in
+the logfile.  In interactive mode, the user may select a different peak with
+the 'z' keystroke, and the maximum peak within the specified \fIwindow\fR
+(centered on the cursor) will be fit.  The user has full control in interactive
+mode over the points used in the fit.  Once the endpoints of the peak have
+been selected, the actual data points are shown with '+' signs on the CCF,
+the fitted curve drawn, and a horizontal bar showing the location of the
+FWHM calculation is displayed.  The status line will show a summary of the 
+fit, and the user may type the 'v' keystroke for a more detailed description
+of the fit and correlation. 
+
+.ih
+VELOCITY COMPUTATION ALGORITHM
+Up to three velocities are computed by the task depending on the completeness
+of the images headers and the presence of dispersion information.  If only
+dispersion information is present, a relative velocity, VREL, and an error
+will be computed.  If a full header is present (see the \fIkeywpars\fR
+help page), an observed and heliocentric velocity (VOBS and VHELIO
+respectively) will be computed.
+
+In short form, here are the equations:
+.nf
+
+    ref_rvobs = catalogue_vel_of_template - H(temp)  # obs. vel. of temp.
+    VREL = C * (10 ** (wpc * shift) - 1.)	     # relative vel.
+    VOBS = ((1+ref_rvobs/C)*(10**(wpc*shift)-1)) * C # observed vel.
+    VHELIO = VOBS + H(object)			     # heliocentric vel.
+
+.fi
+where H() is the heliocentric correction for that observation.  The
+equation used for the relative velocity is derived from the standard
+(1+z), and the VOBS equation reflects that the observed velocty is the
+product of (1+z) values for the object and template (this allows for high
+redshift templates to be used).  The date, time, and position of each
+spectrum is found from the image header via the keywords defined in
+\fIkeywpars\fR.  In the case of the time the task first looks for a
+keyword defining the UT mid-point of the observation
+(\fIkeywpars.utmiddle\fR).   If that is not found any time present in the
+header DATE-OBS (\fIkeywpars.date_obs\fR) keyword is used at the UT start
+point, if there is no time in the keyword value then the mid-point UT is
+computed from the exposure time (\fIkeywpars.exptime\fR) and UT of
+observation (\fIkeywpars.ut\fR) keywords.
+
+The keyword added to the template header (as defined by the
+"vhelio" parameter in the \fIkeywpars\fR pset) should be the catalogue velocity 
+of the template.  Since the observation of the template has a slightly
+different heliocentric correction, this is subtracted from the template
+heliocentric velocity so that the \fIobserved\fR velocity of the template 
+is used when correcting the relative velocity computed from the shift.  
+This gives the \fIobserved\fR velocity of the object wrt the template.  
+Adding the heliocentric correction of the object star then yields the true
+heliocentric velocity of the object.
+
+.bp
+.ih
+CURSOR KEYS AND COLON COMMANDS SUMMARY
+
+.ce
+CORRELATION MODE COMMANDS
+.nf
+?  Print list of cursor key and colon commands
+-  Subtract blended component from correlation peak
+.  Do the continuum subtraction
++  Toggle status line output
+a  Display the antisymmetric noise component of the correlation
+b  Fix the background level for the Gaussian fit
+c  Read out cursor position in pixel lag and velocity
+d  Deblend multiple correlation peak
+e  Preview the summary plot of the correlation
+f  Fourier filtering and FFT display mode
+g  Mark correlation peak lag limits and fit
+I  Interrupt
+j  Plot the residuals of the fit to the peak
+l  Page the current logfile of results
+m  Plot polymarkers of actual CCF points on the plot
+n  Go to next (template --> aperture --> object)
+o  Fit or refit object spectrum continuum for subtraction
+p  Go to previous (template --> aperture --> object)
+q  Quit task
+r  Redraw
+s  Examine object/template spectra and display mode
+t  Fit or refit template spectrum continuum for subtraction
+v  Print full correlation result in text window
+w  Write current correlation results to the log file
+x  Compute correlation
+y  Mark correlation peak lower limit and fit
+z  Expand on different correlation peak using full correlation plot
+
+:apertures [range]               Set/Show list of apertures to process
+:apnum  [aperture]               Set/Show specific aperture to process
+:apodize  [fraction]             Set/Show fraction of endpts to apodize
+:autowrite [y|n]                 Set/Show autowrite param
+:autodraw  [y|n]                 Set/Show autodraw param
+:background  [background|INDEF]  Set/Show background fitting level
+:ccftype  [image|text]           Set/Show type of CCF output
+:comment  [string]               Add a comment to the output logs
+:continuum  [both|obj|temp|none] Set/Show which spectra to normalize
+:correction shift                Convert a pixel shift to a velocity
+:deltav                          Print the velocity per pixel dispersion
+:disp				 Print dispersion info
+:filter  [both|obj|temp|none]    Set/Show which spectra to filter
+:function [gaussian|lorentzian|  Set/Show CCF peak fitting function
+              center1d|parabola]
+:height  [height]                Set/SHow CCF peak fit height
+:imupdate  [y|n]                 Set/Show image update flag
+:maxwidth  [width]               Set/Show min fitting width
+:minwidth  [width]               Set/Show max fitting width
+:nbang                           :Next command without a write
+:next [temp|aperture|object]     Go to next correlation pair
+:objects  [list]                 Set/Show object list
+:osample  [range]                Set/Show object regions to correlate
+:output  [fname]                 Set/Show output logfile
+:<parameter> [value]             Set/Show pset parameter value
+:peak  [y|n]                     Set/Show peak height flag
+:pbang                           :Previous command without a write
+:previous [temp|aperture|object] Go to previous correlation pair
+:printz [y|n]			 Toggle output of redshift z values
+:rebin [small|large|obj|temp]    Set/Show the rebin parameter
+:results [file]                  Page results
+:rsample  [range]                Set/Show template regions to correlate
+:show                            List current parameters
+:templates  [list]               Set/Show template list
+:tempvel  [velocity]             Set/Show template velocity
+:tnum  [temp_code]               Move to a specific temp. in the list
+:unlearn                         Unlearn task parameters
+:update                          Update task parameters
+:version                         Show task version number
+:verbose  [y|n]                  Set/Show verbose output flag
+:wccf                            Write out the CCF to an image|file
+:weights  [weight]               Set/Show fitting weights
+:width  [width]                  Set/Show fitting width about peak
+:wincenter  [center]             Set/Show peak window center
+:window  [size]                  Set/Show size of window
+:ymin  [correlation height]      Set/Show lower ccf plot scaling
+:ymax  [correlation height]      Set/Show upper ccf plot scaling
+.fi
+
+.ce
+FOURIER MODE COMMANDS
+.nf
+?  Print list of cursor key and colon commands
+b  Display power spectra before filtering
+f  Enter Fourier mode
+g  Display Fourier transforms before filtering
+i  Print period trend information
+o  Display filtered and unfiltered object spectrum
+p  Display power spectra after filtering
+q  Quit
+r  Redraw
+s  Enter Spectrum mode
+t  Display filtered and unfiltered template spectrum
+x  Return to parent mode
+
+:log_scale [y|n]              Plot on a Log scale?
+:one_image [object|template]  What plot on screen
+:overlay [y|n]                Overlay filt function?
+:<parameter> [value]          Set/Show the FILTERPARS parameter value
+:plot [object|template]       What type of plot to draw on single plot? 
+:split_plot [y|n]             Make a split-plot?               
+:when [before|after]          Plot before/after filter?   
+:zoom [factor]                FFT zoom parameter
+.fi
+
+.ce
+CONTINUUM MODE COMMANDS
+
+See \fBicfit\fR.
+
+.ce
+SPECTRUM MODE COMMANDS
+.nf
+?  Print list of cursor key and colon commands
+b  Select sample regions for both spectra
+d  Print velocity difference between two cursor positions
+f  Enter Fourier mode
+i  Display original input spectra
+n  Display continuum subtracted spectra
+p  Display the prepared spectra prior to correlation
+q  Quit
+r  Redraw
+s  Select sample region endpoints
+u  Unselect a sample region
+x  Return to correlation mode
+
+:<parameter> [value]    Set/Show parameters in CONTINPARS pset
+:osample [list]         List of object sample regions
+:rsample [list]         List of template sample regions
+:show                   List current parameters
+.fi
+
+.ih
+EXAMPLES
+.nf
+    1. Cross correlate a list of 1-dimensional object spectra against
+    three 1-dimensional template spectra, saving results automatically
+    and not continuum subtracting or filtering the data:
+
+	rv> fxcor.interactive = no		# Do it in batch mode
+	rv> fxcor obj* temp1,temp2,temp3 autowrite+ continuum="no"
+	>>> filter="no" output="results"
+
+    2. Compute a velocity for a list of apertures in a 2-dimensional 
+    multispec format object image, using only two apertures of a multispec
+    image as the templates:
+
+	cl> onedspec
+	on> scopy object.ms temp apert="8,9" inform="multi" outform="oned"
+	on> rv
+	rv> fxcor.interactive = no		# Do it in batch mode
+	rv> fxcor object.ms temp.0008,temp.0009 apertures="1-7,10,12-35"
+
+    In this example, apertures 8 and 9 of the object image will be used 
+    as the template.  The \fIscopy\fR task is used to extract the aper-
+    tures to onedspec format, into two images named "temp.0008" and 
+    "temp.0009".  The task is then run with all of the apertures in the 
+    aperture list correlated against the onedspec templates.
+
+    3. Compute a velocity by fitting a fixed number of points on the peak,
+    using uniform weighting:
+
+	rv> fxcor obj temp width=8 weights=0.
+
+    4. Compute a velocity by fitting a Gaussian to the points on the CCF
+    peak above the 0.1 correlation level.  Constrain the number of points
+    to be less than 15, and linearly decrease the weights:
+
+	rv> fxcor obj temp func="gaussian" width=INDEF height=0.1 
+	>>> maxwidth=15 weights=1.
+
+    5. Compute a velocity by fitting a Lorentzian to the peak, from the
+    peak maximum to it's half power point:
+
+	rv> fxcor obj temp func-"lorentz" width=INDEF height=0.5 peak+
+	>>> maxwidth=15 weights=1.
+
+    6. Process a 1-dimensional object against a 1-dimensional template
+    interactively, examining the FFT, and input spectra to define a sample
+    region for the correlation:
+
+	rv> fxcor obj temp inter+ continuum="both" autowrite- output=""
+	    Screen is cleared and CCF peak with fit displayed
+
+	... to refit peak, move cursor to left side of peak and type 'g'
+	... move cursor to right side of peak and hit any key
+
+	    New fit is drawn and results displayed to the status line
+
+	... type the 'v' key for a detailed description of the correlation
+
+	    Graphics are suspended and the text screen shows various
+	    parameters of the correlation and fit. 
+
+	... type 'q' to get back to graphics mode
+
+	... to examine the FFT's of the spectra, type the 'f' keystroke.
+
+	    The screen is cleared and a split plot of the two power spectra
+	    after filtering is drawn with the requested filter (if any)
+	    overlayed.
+	... type the 'f' keystroke
+	    The screen is cleared and the absolute value of the two FFT's
+	    after filtering is plotted, again with the filter overlayed.
+	... type ":overlay no", followed by a 'g' keystroke
+	    The spectra are redrawn prior to filtering, with no filter over-
+	    lay
+	... type 'q' to return to correlation mode
+
+	    The screen is redrawn with the CCF plot and peak fit
+
+	... type 's' to enter spectrum mode
+
+	    The screen is cleared and the input spectra displayed
+	... type 's' to mark the endpoints of sample regions for correl-
+	... ation.  The user can mark either the top or bottom plot to
+	... set sample regions for the object and template respectively.
+	... Then type 'q' to quit this mode
+
+	    A new correlation is computed and the peak refit automatically
+
+	... type 'q' to quit the task, satisfied with the results
+	    The user is asked whether he wants to save results
+	... type 'y' or <cr> to save results
+	    The user is prompted for an output file name since one wasn't
+	    specified in the parameter set
+	... type in a file name
+	 
+	    The task exits.
+
+    7. Save the correlation function of two galaxy spectra: 
+
+	rv> fxcor obj temp inter+ ccftype="text"
+	    Screen is cleared and CCF peak with fit displayed
+
+	... type ":wccf" to write the CCF
+	... type in a filename for the text output
+	... quit the task
+
+	rv> rspectext ccf.txt ccf.fits dtype=interp
+	rv> splot ccf.fits
+
+       The velocity per-pixel-shift is non-linear and is an approximation
+       which works well for low-velocity shifts.  In the case of hi-velocity
+       correlations (or when there are many points) it is best to save the
+       CCF as a text file where the velocity at each shift is written to
+       the file,  then use RSPECTEXT to linearize and convert to an image
+       format.  This avoids the task interpolating a saved image CCF in
+       cases where it may not be required.
+
+    7. Compute a cross-correlation where the template has already been
+       corrected to the rest frame and no heliocentric correction is 
+       required:
+
+	  Step 1)  Use the HEDIT or HFIX tasks to add the following
+		   keywords to the template image:
+
+		        DATE-OBS= '1993-03-17T04:56:38.0'
+		        RA      = '12:00:00'
+		        DEC     = '12:00:00'
+		        EPOCH   = 1993.0
+		        OBSERVAT= 'KPNO'
+		        VHELIO  = 0.0
+
+		   These values produce a heliocentric correction of zero
+		   to within 5 decimal places.  The VHELIO keyword will 
+		   default to zero if not present.
+
+	  Step 2)  Use the HEDIT task to add an OBSERVAT keyword to each
+		   of the object spectra.  The OBSERVATORY task can be used
+		   get a list of recognized observatories.
+
+	Because mixing observatories is not currently well supported, the
+	use of the OBSERVAT keyword in \fI both\fR images is the only sure
+	way to apply the proper observatory information to each image.  Users
+	may wish to derive a zero-valued heliocentric correction for their
+	local observatory and use those values instead.
+.fi
+
+.ih
+SEE ALSO
+continpars, filtpars, observatory, keywpars, onedspec.specwcs, center1d, 
+dispcor, stsdas.fourier
+.endhelp
diff --git a/noao/rv/doc/keywpars.hlp b/noao/rv/doc/keywpars.hlp
new file mode 100644
index 00000000..5fd1aa9f
--- /dev/null
+++ b/noao/rv/doc/keywpars.hlp
@@ -0,0 +1,94 @@
+.help keywpars Dec90 noao.rv
+.ih
+NAME
+keywpars -- edit the image header keywords used by the package
+.ih
+USAGE
+keywpars
+.ih
+PARAMETERS
+.ls ra = "RA"
+Right Ascension keyword. (Value in HMS format).
+.le
+.ls dec = "DEC"
+Declination keyword. (Value in HMS format).
+.le
+.ls ut = "UT"
+UT of observation keyword.  This field is the UT start of the observation.
+(Value in HMS Format).
+.le
+.ls utmiddle = "UTMIDDLE"
+UT mid-point of observation keyword.  This field is the UT mid-point of 
+the observation.  (Value in HMS Format).
+.le
+.ls exptime = "EXPTIME"
+Exposure time keyword. (Value in Seconds).
+.le
+.ls epoch = "EPOCH"
+Epoch of coordinates keyword. (Value in Years).
+.le
+.ls date_obs = "DATE-OBS"
+Date of observation keyword.  Format for this field should be
+dd/mm/yy, (old FITS format), yyyy-mm-dd (new FITS format), or
+yyyy-mm-ddThh:mm:ss.sss (new FITS format with time).
+.le
+
+.ce 
+OUTPUT KEYWORDS
+.ls hjd = "HJD"
+Heliocentric Julian date keyword. (Value in Days).
+.le
+.ls mjd_obs = "MJD-OBS"
+Modified Julian Data keyword.  The MJD is defined as the julian date of
+the mid-point of the observation - 2440000.5.  (Value in Days).
+.le
+.ls vobs = "VOBS"
+Observed radial velocity keyword.  (Value in Km/sec).
+.le
+.ls vrel = "VREL"
+Observed radial velocity keyword. (Value in Km/sec).
+.le
+.ls vhelio = "VHELIO"
+Corrected heliocentric radial velocity keyword.  (Value in Km/sec).
+.le
+.ls vlsr = "VLSR"
+Local Standard of Rest velocity keyword.  (Value in Km/sec).
+.le
+.ls vsun = "VSUN"
+Epoch of solar motion.  (Character string with four real valued fields 
+describing the solar velocity (km/sec), the RA of the solar velocity (hours),
+the declination of the solar velocity (degrees), and the epoch of solar
+coordinates (years)).
+.le
+.ih
+DESCRIPTION
+The image header keywords used by the \fIfxcor\fR task can be 
+edited if they differ
+from the NOAO standard keywords.  For example, if the image header keyword
+giving the exposure time for the image is written out as "EXP-TIME" instead
+of the standard "OTIME" at a given site, the keyword accessed for 
+that information
+may be changed based on the value of the \fIexptime\fR parameter.
+
+The \fIvhelio\fR keywords must be added to the image header of the template 
+spectrum and should contain the known radial velocity of the template star.
+The output keywords may be added to the object image header if the
+tasks \fIfxcor.imudate\fR parameter is set.
+
+.ih
+EXAMPLES
+1. List the image header keywords.
+
+.nf
+	rv> lpar keywpars
+.fi
+
+2. Edit the image header keywords
+
+.nf
+	rv> keywpars
+.fi
+.ih
+SEE ALSO
+fxcor
+.endhelp
diff --git a/noao/rv/doc/rv.spc b/noao/rv/doc/rv.spc
new file mode 100644
index 00000000..720f1b0b
--- /dev/null
+++ b/noao/rv/doc/rv.spc
@@ -0,0 +1,918 @@
+.help rvxcor Aug90 noao.rv
+.ih
+INTRODUCTION
+
+Specifications are presented for a Fourier cross-correlation task used
+to compute either relative or heliocentric radial velocities.  Input
+data need not be dispersion corrected, and the user has full control
+over cross-correlation function (ccf) peak fitting, continuum subtraction,
+and Fourier filtering of the data.  Several sub-modes exist wherein the
+user may examine the Fourier characteristics of the data, interactively
+fit the continuum, and examine the input spectra themselves.  Output
+options include a text logfile which may be parsed with the IRAF \fIfields\fR
+task, a GKI metacode file containing a summary plot of the correlation,
+and optionally a text or IRAF image of the ccf itself (from interactive 
+operation only).
+
+.ih
+SUMMARY
+.nf
+
+			BASIC TASK ORGANIZATION
+			
+		  List of object and template spectra
+				|
+				|	      +------------------------+
+				|	      | Rebin the data?	       |
+		       +--------------+       | Fit/subtract continuum |
+		       | Prepare data |<----->| Zero endpoints and pts |
+		       +--------------+       |     not in sample      |
+				|	      | Subtract bias          |
+		                |     	      | Apodize end regions    |
+		    +----------------------+  | Center in FFT array    |
+		    | Compute correlation  |  +------------------------+
+		    | Display correlation  |
+		    | Fit correlation peak |
+		    +----------------------+
+				|
+	   +--------------------+-----------------------+
+	   ^			^		   	^
+	  / \   	       / \      	       / \
+	   |			|		   	|
+	  \ /   	       \ /      	       \ /
+	   `			`			`
++-------------------+   +---------------------+   +-------------------+
+| Fourier filtering |-->| Spectra review      |-->| Continuum fitting |
+|		    |<--| Mark sample regions |<--| ICFIT             |
++-------------------+   +---------------------+   +-------------------+
+
+			TASK PARAMETERS
+
+Input parameters:	objects
+			templates
+			apertures = "*"
+			cursor = ""
+
+Data preparation:	continuum = "both"
+			filter = "none"
+			sample = "*"
+			apodize = 0.2
+
+Peak fitting:		function = "gaussian"
+			width = INDEF
+			height = 0.0
+			peak = no
+			minwidth = 3.
+			maxwidth = 11.
+			weights = 1.0
+			background = 0.0
+			window = 20
+
+Output parameters:	output = ""
+			verbose = "yes"
+			imupdate = "no"
+			graphics = "stdgraph"
+
+Control parameters:	interactive = "yes"
+			autowrite = "yes"
+			ccftype = "image"
+
+Parameter sets:		continpars = ""
+			filterpars = ""
+			rvkeywords = ""
+			observatory = ""
+
+MAIN CORRELATION FITTING COMMAND SUMMARY
+
+?  Print list of cursor key and colon commands
+-  Subtract blended component from correlation peak
++  Toggle status line output
+a  Display the antisymmetric noise component of the correlation
+b  Fix background level for Gaussian fit
+c  Plot polymarkers of actual CCF points on the plot
+d  Deblend multiple correlation peak
+e  Preview the summary plot of the correlation
+f  Fourier filtering and display mode
+g  Mark correlation peak lag limits and fit
+j  Plot the residuals of the fit to the peak
+k  Plot the ratio of the fit to the peak
+l  Page the log file of results
+n  Go to next (template --> aperture --> object)
+o  Fit or refit object spectrum continuum for subtraction
+p  Go to previous (template --> aperture --> object)
+q  Quit task
+r  Redraw
+s  Examine object/template spectra and display mode
+t  Fit or refit template spectrum continuum for subtraction
+v  Print full correlation results in text window
+w  Write current correlation results to the log file
+x  Compute a new correlation
+y  Mark correlation peak lower limit and fit
+z  Expand on different correlation peak using full correlation plot
+
+:next [template|aperture|object]	Go to next correlation pair
+:parameters				List current parameters
+:previous [template|aperture|object]	Go to previous correlation pair
+:results [file]				Page results
+:wccf file				Write the CCF to an image/text file
+
+Other colon commands set or show parameter values
+
+FOURIER FILTERING COMMAND SUMMARY
+
+?  Print list of cursor key and colon commands
+b  Display power spectra before filtering
+f  Display Fourier transforms after filtering
+g  Display Fourier transforms before filtering
+i  Print period trend information
+p  Display power spectra after filtering
+q  Quit
+r  Redraw
+s  Enter spectrum mode
+x  Return to correlation mode
+
+:log_scale [yes|no]		Set log scaling on Y axis
+:overlay [yes|no]		Overlay filter function
+:parameters			List current parameter values
+:zoom [factor]			Zoom x region
+
+Other colon commands set or show parameter values
+
+SPECTRUM REVIEW COMMAND SUMMARY
+
+?  Print list of cursor key and colon commands
+d  Print velocity difference between two cursor positions
+e  Plot a preview of the summary plot
+f  Enter Fourier mode
+i  Display original input spectra
+n  Display continuum subtracted spectra
+q  Quit
+r  Redraw
+s  Mark sample regions 
+x  Return to correlation mode
+
+:sample [list]			List of sample regions
+
+CONTINUUM FITTING COMMAND SUMMARY
+
+See \fBicfit\fR.
+.fi
+.bp
+.ih
+NAME
+rvxcor -- compute radial velocities via Fourier cross correlation
+.ih
+USAGE
+rvxcor objects templates
+.ih
+PARAMETERS
+.ce
+INPUT PARAMETERS
+.ls objects
+The list of image names for the input object spectra.
+.le
+.ls templates
+The list of image names that will be used as templates for the cross
+correlation.
+.le
+.ls apertures = "*"
+List of apertures to be used.  This number is used for \fIboth\fR the
+object and reference spectra. A '*' means to process all of the
+apertures in the spectrum.  If the template spectrum is one-dimensional, 
+that spectrum will be used as a template for all specified apertures in 
+the object spectrum.
+.le
+.ls cursor = ""
+Graphics cursor input.
+.le
+
+.ce
+DATA PREPARATION PARAMETERS
+.ls continuum = "both"
+Continuum subtract the spectra prior to correlation?  Possible values for
+this parameter are any of the strings (or abbreviations) "object" (for object 
+spectrum only), "template" (for template spectrum only), or "both" for 
+continuum flattening both object and template spectra, or simply "none" for 
+flattening neither spectrum.  The \fIcontinpars\fR pset is used to specify 
+the continuum fitting parameters.
+.le
+.ls filter = "none"
+Fourier filter the spectra prior to correlation?  Possible values for
+this parameter are any of the strings (or abbreviations) "object" (for object 
+spectrum only), "template" (for template spectrum only), or "both" for 
+fourier filtering both object and template spectra, or simply "none" for 
+filtering neither spectrum.  The \fIfilterpars\fR pset holds the parameters 
+for the filtering (filter type and width).
+.le
+.ls sample = "*"
+Sample regions of the spectrum to be used in the correlation specified
+in pixels if the first character is a 'p' or angstroms if the first
+character is an 'a'.  The default (i.e. no 'a' or 'p' as the first
+character), if a range is provided, is a range specified in pixels.
+This string value will be updated in an interactive session as sample
+regions are re-selected. The default, '*', is the entire spectrum.  The
+region is specified as a starting value, a '-', and an ending value.
+.le
+.ls apodize = 0.2
+Fraction of endpoints to apodize with a cosine bell when preparing the data
+prior to the FFT.
+.le
+
+.ce
+CORRELATION PEAK FITTING PARAMETERS
+.ls function = "gaussian"
+Function used to find the center and width of the correlation peak.
+Possible choices are "gaussian", "parabola", "lorentzian", or "center1d".
+If a parabola or center1d fit is selected then only the center is determined.
+.le
+.ls width = INDEF
+Width of the fitting region in pixels.  The fitting weights are
+zero at the endpoints so the width should be something
+like the expected full width.  If INDEF, then the width is
+set by the \fIheight\fR and \fIpeak\fR parameters. If other than INDEF, 
+this parameter will override the \fIheight\fR and \fIpeak\fR parameters.
+It is recommended that an odd value of \fIwidth\fR be used to assure an
+even number of pixels around the peak height.
+.le
+.ls height = 0.
+The width of the fitting region is defined by where the correlation
+function crosses this height starting from the peak.  The height is
+specified as either a normalized correlation level (this is like
+the 'y' interactive key) or normalized to the peak.  The type of
+level is selected by the peak parameter.
+.le
+.ls peak = no
+Measure the height parameter relative to the correlation peak value
+rather than as a normalized correlation level? If yes, then \fIheight\fR
+is a fraction of the peak height with an assumed base of zero.
+.le
+.ls minwidth = 3., maxwidth = 11.
+The minimum and maximum widths allowed when the width is determined
+from the height.
+.le
+.ls weights = 1.
+Power of distance defining the fitting weights.  The points used
+in fitting the correlation peak are weighted by a power of the
+distance from the center as given by the equation
+.nf
+
+         1 - (distance / (width/2)) ** weights
+
+.fi
+Note that a weight parameter of zero is equivalent to uniform weights.
+The center1d fitting algorithm uses it's own weighting function.
+.le
+.ls background = 0.0
+Background level, in normalized correlation units, for a Gaussian or 
+Lorentzian fitting function.  If set to INDEF, the background is a free 
+parameter in the fit.
+.le
+.ls window = 20
+Size of the window in the correlation plot.  The peak will be displayed
+with a window centered on the peak maximum and two times \fIwindow\fR 
+lags wide.
+.le
+
+.ce
+OUTPUT PARAMETERS
+.ls output = ""
+File name of file to which output will be written.  If no file name is given
+then no log files will be kept, but the user will be queried for a file name
+if a write operation is performed.  Text output will have a ".txt" sufix 
+appended, and the graphics metacode file will be appended with a ".gki" suffix.
+.le
+.ls verbose = "yes"
+Print a verbose output record to the \fIoutput\fR file?  The verbose output
+will be a single line ~160 characters wide.  The \fIfields\fR task may
+be used to strip out selected columns.  Non-verbose output is ~80 chars wide.
+.le
+.ls imupdate = "no"
+Update the image header with the computed velocities?  If set to yes, then
+the image will be updated with the observed and heliocentric velocities
+by adding the \fIrvkeywords.vobs\fR and \fIrvkeywords.vhelio\fR keywords
+respectively.  Two-dimensional spectra will have the keywords added with 
+the aperture number appended to the keyword.
+.le
+.ls graphics = "stdgraph"
+Output graphics device.
+.le
+
+.ce
+CONTROL PARAMETERS
+.ls interactive = "yes"
+Process spectra interactively?  
+.le
+.ls autowrite = "yes"
+Automatically record the last fit to the log file when moving to the next
+spectrum?  If set to "no", the user will be queried whether to write the
+results if no write was performed, and possibly queried for a file name 
+if \fIoutput\fR isn't set.  
+.le
+.ls ccftype = "image"
+Type of output to create when writing out the correlation function with
+the ":wccf file" command.  Possible choices are "text" which will be a
+simple list of (lag,correlation_value) pairs, or "image" which will be an
+IRAF image whose header would describe the lag limits and selected peak.
+.le
+
+.ce
+ADDITIONAL PARAMETER SETS
+.ls continpars = ""
+The processing parameters as described in the \fIcontinpars\fR named pset.
+.le
+.ls filterpars = ""
+This is a parameter set defining the parameters to be used in filtering the
+data prior to the correlation. 
+.le
+.ls rvkeywords = ""
+The image header keyword translation table as described in 
+the \fIrvkeywords\fR named pset.
+.le
+.ls observatory = ""
+The observatory parameter set giving the location of the observation.  These
+values are used in the heliocentric correction routines.
+.le
+.ih
+DESCRIPTION
+\fIRvxcor\fR performs a Fourier cross-correlation on the input list of object
+and template spectra.  Object spectra may be either one or two dimensional
+(in `echelle' or `multispec' format), and may be correlated against a one
+or two dimensional template.  If the template spectrum is only one dimensional
+but the object is two dimensional, the template is used to correlate each of
+the apertures specified by the \fIapertures\fR parameter.  Two dimensional
+templates will correlate corresponding apertures.
+
+If the input spectra are not dispersion corrected (DC-FLAG parameter missing
+or less than zero) then only a pixel space correlation is done.  This is
+appropriate for a simple cross-correlation of images whether spectra or not.
+If the spectra are dispersion corrected a log binned correlation is
+performed and various radial velocity measurements are made. At a minimum,
+a relative velocity between the object and template spectra are produced.
+If the image headers contain sufficient information for heliocentric
+velocity corrections (see help for \fBrvkeywords\fR), the corrections are
+computed and possibly recorded in the image header.  If the value of the 
+heliocentric velocity is returned as INDEF, the user may use the 'v'
+keystroke to see the full results of the correlation, including errors
+which occured causing the corrections to not be done.
+
+A number of operations may be performed to prepare the data for
+correlation.  If a linear wavelength dispersion is defined the spectra
+are rebinned to a log-linear dispersion. The starting and ending wavelength, 
+the dispersion in log space, and the number of pixels are determined from
+the template.  If the \fIcontinuum\fR flag is set to sonething other than 
+"none", the object and/or template data will
+be continuum subtracted using the fitting parameters found in the
+\fIcontinpars\fR pset on input.  The data is zeroed outside the sample
+region specified by the \fIsample\fR parameter, the bias is subtracted,
+and the ends apodized.  If the \fIfilter\fR flag is set to something other than
+"none", the data are Fourier filtered according to the parameters in 
+the \fIfilterpars\fR pset prior to the correlation computation.
+
+Once the correlation is computed, the maximum peak is found and fit
+according to the \fIwidth\fR, \fIheight\fR and \fIpeak\fR parameters.
+A small, unlabelled plot of the entire correlation function is 
+drawn above a larger,
+expanded plot centered on the peak in a window of size specified by the
+\fIwindow\fR parameter.  The dashed lines in the small plot
+show the limits of the expanded plot.  The bottom axis is labelled with
+pixel lag and, if dispersion information is present, the top axis
+is labelled with relative velocity.  The status line will contain a
+summary of the pixel shift from the fit and optional velocity
+information.  The 'v' keystroke may be used to suspend graphics and get
+a more detailed description of the correlation and fit. To view the
+antisymmetric noise component of the correlation function, simply hit 
+the 'a' keystroke followed by any keystroke to return to the correlation
+plot. Similarly, the 'e' keystroke may be used to preview the summary
+plot of the correlation, again hitting any key to return to the correlation.
+
+If the user is dissatisfied with the fit to the peak, he can mark the
+left and right side of the peak with the 'g' keystroke to redo the fit,
+or else set the cursor to mark a cutoff with the 'y' keystroke, and all
+points from the peak maximum to the cursor will be fit.  To fix the background
+of a Gaussian fit (i.e. change the \fIbackground\fR parameter graphically), 
+type the 'b' keystroke at the desired level.  To choose a different
+peak to fit, move the cursor to the top plot of the whole ccf and hit the
+'z' keystroke at the desired peak.  The plot will be redrawn with the new
+peak now centered in the window and a fit automatically done.  The 'r'
+keystroke may be used at any time to redraw the plot, and the 'x' keystroke
+can be used to compute a new correlation if any of the parameters relating
+to the correlation are changed
+(e.g. the apodize percentage).  New correlations are automatically computed
+when new images are read in, the data are continuum subtracted, a different
+region is selected for correlation, or Fourier filtering is done.
+
+For binary star work, the user may type the 'd' and/or '-' keystrokes to fit
+and then subtract up to four Gaussians to the peaks.  This feature behaves
+exactly as the deblending functions in the task \fIonedspec.splot\fR.  Consult
+the \fIsplot\fR help page for details.  If multiple peaks were fit, 
+a separate entry
+will be made in the log file for each peak with a comment that it was part of
+a blended peak.  The metacode file will contain only one summary plot with
+each peak marked with it's heliocentric velocity (if velocities requested)
+or pixel shift and error.
+
+To move to the next spectrum, simply hit the 'n' keystroke.  Similary,
+the 'p' keystroke will move to the previous spectrum.  These commands
+have a hitch, though.  By default, the next/previous commands will move
+first to the next template in the template image list.  Once the end of the
+template image list is reached, the next spectrum will be the next aperture
+in the list specified by \fIapertures\fR, resetting the template image list
+automatically and possibly updating the aperture in the template image 
+as well.  Finally, after correlating all of the templates against
+all of the apertures, the next/previous command will move to the next
+object image, again resetting the template image and/or aperture list.
+To override this sequence, the user may use the ":next"
+or ":previous" commands and specify one of "aperture", "object", or
+"template".  If the \fIautowrite\fR is set, the results of the last
+fit will be written to the log automatically.  To write any one of the
+fits explicity, use the 'w' keystroke.
+
+The \fIrvxcor\fR task also contains three submodes discussed in detail below.
+Briefly, the 'f' keystroke will put the user in the "fourier mode",
+where he can examine the Fourier transform of the spectra in various
+ways and change/examine the filtering parameters.  The 'o' and 't'
+keystrokes let the user examine and fit the continuum for the object
+and template spectra, respectively, using the \fBicfit\fR commands.
+Upon exiting the continuum fitting the spectra are continuum subtracted 
+and a new correlation is computed.  Finally the 's' keystroke will put
+the user in "spectrum mode", in which he may graphically select the
+region to be correlated, compute an approximate shift using the cursor,
+or simply examine the two spectra in a variety of ways.  All of these
+submodes are exited with the 'q' keystroke, after which the correlation
+will be redone, if necessary, and the ccf plot redrawn.
+
+To exit the task, the user simply types a 'q' keystroke.  Results will be saved
+to the logfile automatically if one was specified, otherwise the user will
+be asked if he wants to save the results, and if so queried for a file name
+before exiting if no \fIoutput\fR file was defined.
+
+(References: Tonry, J. and Davis, M. 1979 \fIAstron. J.\fR \fB84,\fR 1511, 
+and Wyatt, W.F. 1985 in \fIIAU Coll. No 88, Stellar Radial Velocities\fR, 
+p 123).
+
+.ce
+CURSOR KEYS AND COLON COMMANDS
+
+.nf
+?  Print list of cursor key and colon commands
+-  Subtract blended component from correlation peak
++  Toggle status line output
+a  Display the antisymmetric noise component of the correlation
+b  Fix the background level for the Gaussian fit
+c  Plot polymarkers of actual CCF points on the plot
+d  Deblend multiple correlation peak
+e  Preview the summary plot of the correlation
+f  Fourier filtering and FFT display mode
+g  Mark correlation peak lag limits and fit
+j  Plot the residuals of the fit to the peak
+k  Plot the ratio of the fit to the peak
+l  Page the current logfile of results
+n  Go to next (template --> aperture --> object)
+o  Fit or refit object spectrum continuum for subtraction
+p  Go to previous (template --> aperture --> object)
+q  Quit task
+r  Redraw
+s  Examine object/template spectra and display mode
+t  Fit or refit template spectrum continuum for subtraction
+v  Print full correlation result in text window
+w  Write current correlation results to the log file
+x  Compute correlation
+y  Mark correlation peak lower limit and fit
+z  Expand on different correlation peak using full correlation plot
+
+:next [template|aperture|object]	Go to next correlation pair
+:parameters				List current parameters
+:previous [template|aperture|object]	Go to previous correlation pair
+:results [file]				Page results
+
+Other colon commands set or show parameter values
+.fi
+
+.ih
+FOURIER MODE DESCRIPTION
+Fourier mode is entered from the main task via the 'f' keystroke.  By 
+default, the user is presented with a split plot of the power spectra of
+the object and template spectra (object on top) and the requested filter
+overlayed. The X-axis is double-labelled with wavenumbers on the bottom 
+and frequency on top.  The ":log_scale" command can be used to toggle 
+the log scaling of the Y-axis of the plot, and the ":overlay" command 
+will toggle whether or not the filter function (if specified) is overlayed 
+on the plot.  By default the entire power spectrum is displayed, but 
+the ":zoom" command may be used to specify a blowup factor for the 
+display (e.g. ":zoom 2" will display only the first half of the power 
+spectrum).  Plot scaling parameters are learned for the next invocation 
+of this mode.
+
+The plot contents may also be changed through various keystroke commands.
+The 'p' keystroke will display the power spectrum (the default), the 'f'
+keystroke will display the two FFT's, and the 's' keystroke will display the
+unfiltered and filtered spectra vertically offset.  The 'b' and 'g' 
+keystrokes may be used to examine the power spectra and FFT's 
+respectively \fIbefore\fR filtering.  The user can determine the period 
+trend in the data by placing the cursor at a particular wavenumber/frequency 
+and hitting the 'i' keystroke (this command will not work on a plot of 
+the filtered spectra).  The 'r' key will redraw whichever plot is currently
+selected and a 'q' will return the user to the main task mode.
+
+Colon commands are also used to specify or examine the filtering parameters
+by simply typing a ':' followed by the parameter name found in 
+the \fIfilterpars\fR pset.  The user still has full access to the colon 
+commands in the main task mode.
+
+.ce
+CURSOR KEYS AND COLON COMMANDS
+
+.nf
+?  Print list of cursor key and colon commands
+b  Display power spectra before filtering
+f  Enter Fourier mode
+g  Display Fourier transforms before filtering
+i  Print period trend information
+o  Display filtered and unfiltered object spectrum
+p  Display power spectra after filtering
+q  Quit
+r  Redraw
+s  Display spectra
+t  Display filtered and unfiltered template spectrum
+x  Return to correlation mode
+
+:log_scale [yes|no]		Set log scaling on Y axis
+:overlay [yes|no]		Overlay filter function
+:parameters			List current parameter values
+:zoom [factor]			Zoom x region
+
+Other colon commands set or show parameter values
+.fi
+
+.ih
+CONTINUUM MODE DESCRIPTION
+Automatic continuum subtraction is controlled by the \fIcontinpars\fR
+pset.  These may be reset from the main
+correlation function mode.  To interactively fit and modify the continuum
+fitting parameters the 'o' and 't' keys are used.  This enters
+the ICFIT package which is described elsewhere.  Exiting the fitting,
+with 'q', causes a recomputation of the correlation function and peak
+fit.  To view the flattened spectra use the spectrum review mode
+entered with the 's' key.  Fitting parameters changed while doing the
+interactive continuum fitting are learned.
+
+.ce
+CURSOR KEYS AND COLON COMMANDS
+
+See \fBicfit\fR.
+
+.ih
+SPECTRUM MODE DESCRIPTION
+Spectrum mode is entered from the main task via the 's' keystroke.
+The user may select plots of the original input spectra 'i', the
+continuum subtracted spectra 'n', and the filtered and unfilter spectra 'f'.
+In addition, a sample region for the correlation is
+marked on the bottom of the plots.  To select a new sample region, use the 's' 
+keystroke to select the endpoints of the region.  It may be selected 
+explicity by using the ":sample" command.  The region will be checked to
+see if it lies within the range of the spectrum.  The 'd' keystroke may be
+used to print the difference in pixels (and/or velocity) between two points
+on the spectrum.  This is useful for getting an approximate shift.  
+The 'w' keystroke or ":/<command>" commands will invoke the standard 
+GTOOLS windowing commands.  
+To return to the correlation simply type 'q'.
+
+(NOTE: More functionality is planned for this mode)
+
+.ce
+CURSOR KEYS AND COLON COMMANDS
+
+.nf
+?  Print list of cursor key and colon commands
+d  Print velocity difference between two cursor positions
+f  Enter Fourier mode
+i  Display original input spectra
+n  Display continuum subtracted spectra
+q  Quit
+r  Redraw
+s  Enter Spectrum mode
+w  Window graphs with GTOOLS commands
+x  Return to correlation mode
+
+:sample [list]			List of sample regions
+.fi
+
+.ih
+OUTPUT FILES
+If the \fIoutput\fR parameter is set, two files will be created; one with
+a ".gki" suffix containing metacode output of a summary plot, and one with
+text output in the standard IRAF 'list' format containing either verbose or
+non-verbose output
+having a ".txt" suffix.  If a write operation is performed and no output file
+is specified, the user will be queried for a file name and the files will
+be created.  Text file output may be have selected columns extracted
+using the iraf \fIfields\fR task (where string valued fields will have
+blank spaces replaced with an underscore), and specific metacode plots may
+be extracted or displayed with the iraf \fIgkiextract\fR and/or
+\fIstdgraph\fR/\fIgkimosaic\fR tasks.
+.ls METACODE FILES
+For each correlation fit recorded a metacode plot will be drawn to the file
+named by the \fIoutput\fR parameter with the ".gki" extension.  This plot
+will have a plot of the flattened object spectrum on top, with any selected
+regions for the correlation marked.  The bottom of the plot will be similar 
+to the standard correlation plot, but text will be overlaid showing the fitted
+peak shift, width and computed velocities.
+
+For a blended peak, the plot will be the same with the exception that each of
+the peak components will be labelled with the computed velocity, and the
+text labelling will be suppressed.
+.le
+.ls TEXT FILES
+For each correlation fit recorded a text entry will be written to the file
+named by the \fIoutput\fR parameter with the ".txt" extension.  Regardless
+of whether the file contains verbose output, the file header will have comment
+lines (beginning with a "#" in column 1) identifying each template used
+with a letter code, followed by a description of the image name, template 
+source name, velocity dispersion (which will be the same for the object 
+spectra, and specified velocity.  A similar comment will be written with
+a unique ID whenever a new template image is read into the task interactively.
+Similar comments will also be written to identify error codes, abbreviations
+used, column headings, and the region used in the correlation.
+.ls NON-VERBOSE OUTPUT
+(NOTE: Details about field width and such will be worked out later on...)
+
+Non-verbose output will contain the object image name, object source name 
+(usually the star name), heliocentric Julian data, aperture number,
+a code field identifying whether the data were
+filtered, type of fitting function, and/or continuum subtracted, the pixel
+shift (and error), velocity FWHM, observed velocity, heliocentric
+velocity, and velocity error, as well as an error code field.
+
+This output will extend approximately less than 80 characters.
+.le
+.ls VERBOSE OUTPUT
+(NOTE: Details about field width and such will be worked out later on...)
+
+Verbose text output will contain all of the above fields in the header.
+Also written will be the Tonry & Davis "R" value, correlation peak height,
+FWHM error, and covariance of the correlation.
+
+This output will extend approximately less than 160 characters.
+.le
+.le
+
+.ih
+ALGORITHM DISCUSSIONS
+.ih
+SUMMARY OF THE BASIC TASK STRUCTURE
+In this section we discuss the steps taken in preparing and filtering the
+data prior to the correlation computation.  We will use pseudocode to describe
+this process as it is more detailed than the graphical display shown earlier.
+
+.nf
+begin
+	# Data Rebinning on input
+	IF (DC-FLAG flag does not exist in object)
+	    DC-FLAG(object) = -1
+	IF (DC-FLAG flag does not exist in template)
+	    DC-FLAG(template) = -1
+	IF (DC-FLAG(object) * DC-FLAG(template) < 0)
+	    Print error and go on to next correlation pair
+	ELSE {
+	    IF (DC-FLAG exists in template header && DC-FLAG >= 0)
+	       rebin data to log-linear dispersion
+	    IF (DC-FLAG exists in object header && DC-FLAG >= 0)
+	       rebin to log-linear using template wpc and npts values
+	}
+
+	# Continuum normaliztion and data preparation
+	IF (continuum == "object" || continuum == "both")
+	    fit and subtract the object continuum
+	IF (continuum == "template" || continuum == "both")
+	    fit and subtract the template continuum
+	FOR (object and template spectrum) {
+	    zero non-overlapping points
+	    zero points outside sample region
+	    subtract the bias
+	    apodize remaining data 
+	    center in FFT array of length 2^N
+	    normalize data by the number of FFT points
+	}
+
+	# Do the Fourier filtering
+	compute the FFT of both object and template
+	IF (filter == "object" || filter == "both")
+	    multiply specified filter by object FFT
+	IF (filter == "template" || filter == "both")
+	    multiply specified filter by template FFT
+
+	calculate the cross correlation
+
+	# Get interactive use set up
+	display the ccf to the screen
+	select max peak in ccf
+	determine fit endpoints from "height" (and "nfit"/"threshold") params
+	Fit the selected peak
+	IF (sufficient header information) 
+	    compute heliocentric velocity from pixel shift
+	ELSE
+	    compute only a relative velocity from pixel shift
+	print results to the status line
+
+	# Process the interactive cursor commands
+	REPEAT {
+	    # A few example commands
+	    SWITCH (cursor command) {
+			:
+	    CASE 'f':
+		enter Fourier mode
+			:
+	    CASE 'o':
+		enter ICFIT for object spectrum continuum removal
+			:
+	    CASE 's':
+		enter Spectrum mode
+			:
+	    CASE 't':
+		enter ICFIT for template spectrum continuum removal
+	    }
+	}
+end
+.fi
+.ih
+PEAK FITTING ALGORITHM
+Determining the center of the cross correlation peak is the key step in
+measuring a relative shift or velocity between the object and template.
+The width of the correlation peak is also of interest for measuring
+a line broadening between the two samples.  Since people have different
+preferences and prejudices about these important measurement a variety
+of methods with a range of parameters is provided.
+
+In all cases one must specify the fitting function and a sample width;
+i.e. the range of points about the correlation peak to be used in the
+measurement.  Note that the width defines where the fitting weights
+vanish and should be something like the full width.  For the CENTER1D
+algorithm the maximum weights are at the half width points while for the
+other methods greater weight is given to data nearer the center.
+
+The width may be specified in three ways.  The first is as an actual
+width in pixels.  This is the most straightforward and is independent
+of quirks in the actual shape of the peak.  The second way is to find
+where the correlation function crosses a specified height or level.
+The height may be specified in normalized correlation units or as a
+fraction of the peak height.  The former is equivalent to the
+interactive 'y' key setting while the latter may be used to select some
+"flux" point.  A value of 0.5 in the latter would be approximately the
+full widht at half intensity point except that the true zero or base of
+the peak is somewhat uncertain and one needs to keep in mind that the
+weights go to zero at this point.  Note that a level may be negative.
+In this method the actual width may go to zero or include the entire
+data range if the level fall above the peak or below the minimum of the
+correlation.  The minimum and maximum width parameters are applied to
+constrain the fitting region.  The last method is to interactively mark
+the fitting region with the 'g' key.  A note will be made in the logfile
+if an inflection of the peak is found within the sample range, indicating
+a possible second peak or binary component.
+
+There are four methods for determining the correlation peak position.
+The CENTER1D algorithm has been heavily used in IRAF and is quite
+stable and reliable.  It is independent of a particular model for the
+shape of the peak or the background determination and is based on
+bisecting the integral.  It uses antisymmetric weights with maxima
+at points half way between the estimated center and the fitting
+region endpoint.  A parabola fit is also independent of background
+determinations and also does not determine a width.  It is included
+because it is a common method of peak centering.
+
+The gaussian and lorentzian function fits are model dependent and
+determine a center, width, and peak value.  The background may also
+be determined simultaneously but this extra degree of freedom
+for a function which is not strictly gaussian or lorentzian may
+produce results which are sensitive to details of the shape of the
+correlation function.  The widths reported are the full width at
+half maximum from the fits.
+
+The parabola, gaussian, and lorentzian methods use weights which
+vary continuously from 1 at the estimated center to zero at the
+endpoints of the fitting region.  The functional form of the
+weights is a power law with specified exponent.  A value of zero
+for the exponent produces uniform weights.  However, this is
+discontinuous at the endpoints and so is very sensitive to the data
+window.  A value of one (the default) produces linearly decreasing weights.
+
+All these methods produce centers which depend on the actual
+data points and weights used.  Thus, it is important to iterate
+using the last determined center as the center of the data window
+with continuous weights in order to find a self-consistent center.
+The methods are iterated until the center does not change by more
+than 0.01 pixels or a maximum of 100 iterations is reached.
+
+Errors in the pixel shift are computed from the center parameter of the fitting
+function.  Velocity errors are computed based on the fitted peak height and
+the antisymmetric noise as described in the Tonry & Davis paper (1979,
+\fIAstron. J.\fR \fB84,\fR 1511). Dispersion/pixel-width errors are computed 
+similarly.
+
+The initial peak fit will be the maximum of the ccf.  This will be the only 
+peak fit in non-interactive mode but a confidence level will be entered in
+the logfile.  In interactive mode, the user may select a different peak with
+the 'z' keystroke, and the maximum peak within the specified \fIwindow\fR
+(centered on the cursor) will be fit.  The user has full control in interactive
+mode over the points used in the fit.  Once the endpoints of the peak have
+been selected, the actual data points are shown with '+' signs on the ccf,
+the fitted curve drawn, and a horizontal bar showing the location of the
+FWHM calculation is displayed.  The status line will show a summary of the 
+fit, and the user may type the 'v' keystroke for a more detailed description
+of the fit and correlation. 
+
+.ih
+EXAMPLES
+.nf
+    1. Cross correlate a list of 1-dimensional object spectra against
+    three 1-dimensional template spectra, saving results automatically
+    and not continuum subtracting or filtering the data:
+
+	rv> rvxcor.interactive = no		# Do it in batch mode
+	rv> rvxcor obj* temp1,temp2,temp3 autowrite+ continuum="no"
+	>>> filter="no" output="results"
+
+    2. Compute a velocity for a list of apertures in a 2-dimensional 
+    multispec format object image, using only one aperture of a multispec
+    image as a template:
+
+	rv> rvxcor.interactive = no		# Do it in batch mode
+	rv> rvxcor object.ms temp.ms[*,35:35] apertures="1-7,10,12-35"
+
+    3. Compute a velocity by fitting a fixed number of points on the peak,
+    using uniform weighting:
+
+	rv> rvxcor obj temp width=8 weights=0.
+
+    4. Compute a velocity by fitting a Gaussian to the points on the ccf
+    peak above the 0.1 correlation level.  Constrain the number of points
+    to be less than 15, and linearly decrease the weights:
+
+	rv> rvxcor obj temp func="gaussian" width=INDEF height=0.1 
+	>>> maxwidth=15 weights=1.
+
+    5. Compute a velocity by fitting a Lorentzian to the peak, from the
+    peak maximum to it's half power point:
+
+	rv> rvxcor obj temp func-"lorentz" width=INDEF height=0.5 peak+
+	>>> maxwidth=15 weights=1.
+
+    6. Process a 1-dimensional object against a 1-dimensional template
+    interactively, examining the FFT, and input spectra to define a sample
+    region for the correlation:
+
+	rv> rvxcor obj temp inter+ continuum="both" autowrite- output=""
+	    Screen is cleared and ccf peak with fit displayed
+
+	... to refit peak, move cursor to left side of peak and type 'g'
+	... move cursor to right side of peak and hit any key
+
+	    New fit is drawn and results displayed to the status line
+
+	... type the 'v' key for a detailed description of the correlation
+
+	    Graphics are suspended and the text screen shows various
+	    parameters of the correlation and fit. 
+
+	... type 'q' to get back to graphics mode
+
+	... to examine the FFT's of the spectra, type the 'f' keystroke.
+
+	    The screen is cleared and a split plot of the two power spectra
+	    after filtyering is drawn with the requested filter overlayed.
+	... type the 'f' keystroke
+	    The screen is cleared and the absolute value of the two FFT's
+	    after filtering is plotted, again with the filter overlayed.
+	... type ":overlay no", followed by a 'g' keystroke
+	    The spectra are redrawn prior to filtering, with no filter over-
+	    lay
+	... type 'q' to return to correlation mode
+
+	    The screen is redrawn with the ccf plot and peak fit
+
+	... type 's' to enter spectrum mode
+
+	    The screen is cleared and the the input spectra displayed
+	... type 's' to mark the endpoints of a sample region for correl-
+	... ation.  Then type 'q' to quit this mode
+
+	    A new correlation is computed and the peak refit automatically
+
+	... type 'q' to quit the task, satisfied with the results
+	    The user is asked whether he wants to save results
+	... type 'y' or <cr> to save results
+	    The user is prompted for an output file name since one wasn't
+	    specified in the parameter set
+	... type in a file name
+	 
+	    The task exits.
+.fi
+
+.ih
+TIME REQUIREMENTS
+To be determined
+
+.ih
+SEE ALSO
+continpars, filterpars, observatory, rvkeywords, center1d
+.bp
+.endhelp
diff --git a/noao/rv/doc/rvidlines.hlp b/noao/rv/doc/rvidlines.hlp
new file mode 100644
index 00000000..2e87a412
--- /dev/null
+++ b/noao/rv/doc/rvidlines.hlp
@@ -0,0 +1,530 @@
+.help rvidlines Aug93 noao.rv
+.ih
+NAME
+rvidlines -- Measure radial velocities from spectral lines
+.ih
+USAGE
+rvidlines images
+.ih
+PARAMETERS
+.ls images
+List of spectral images in which to identify spectral lines and measure a
+velocity.  The spectra must be dispersion calibrated in Angstroms.
+.le
+.ls section = "middle line"
+If an image is not one dimensional or given as a one dimensional image
+section then the image section given by this parameter is used.  The
+section is used to define the initial vector and the direction (columns,
+lines, or "z") of the image vectors to be fit.  The image is still considered
+to be two or three dimensional and it is possible to change the data vector
+within the program.
+
+The section parameter may be specified directly as an image section or
+in one of the following forms
+
+.nf
+line|column|x|y|z first|middle|last|# [first|middle|last|#]]
+first|middle|last|# [first|middle|last|#] line|column|x|y|z
+.fi
+
+where each field can be one of the strings separated by | except for #
+which is an integer number.  The field in [] is a second designator
+which is used with 3D data.  See the example section for examples of
+this syntax.  Abbreviations are allowed though beware
+that 'l' is not a sufficient abbreviation.
+.le
+.ls database = "database"
+Database in which the feature data and redshifts are recorded.
+.le
+.ls coordlist = ""
+User coordinate list consisting of an ordered list of rest spectral line
+coordinates.  If a line list is defined lines from the list may be
+automatically found and added to the lines being measured.
+.le
+.ls nsum = "10"
+Number of lines, columns, or bands across the designated vector axis to be
+summed when the image is a two or three dimensional spatial spectrum.
+It does not apply to multispec format spectra.  If the image is three
+dimensional an optional second number can be specified for the higher
+dimensional axis  (the first number applies to the lower axis number and
+the second to the higher axis number).  If a second number is not specified
+the first number is used for both axes.
+.le
+.ls match = 5.
+The maximum difference for a match between the measured line coordinate
+and a coordinate in the coordinate list.  The units of this parameter
+is that of the user coordinates.
+.le
+.ls maxfeatures = 50
+Maximum number of the strongest features to be selected automatically from
+the coordinate list (function 'l') or from the image data (function 'y').
+.le
+.ls zwidth = 100.
+Width of graphs, in user coordinates, when in zoom mode (function 'z').
+.le
+
+The following parameters are used in determining feature positions.
+.ls ftype = "absorption" (emission|absorption|gemission|gabsorption)
+Type of features to be identified.  The possibly abbreviated choices are
+"emission", "absorption", "gemission", and "gabsorption".  The first two
+select the \fBcenter1d\fR centering algorithm while the last two
+select the Gaussian fitting centering algorithm.
+.le
+.ls fwidth = 4.
+Width in pixels of features to be identified.
+.le
+.ls cradius = 5.
+The maximum distance, in pixels, allowed between a feature position
+and the initial estimate when defining a new feature.
+.le
+.ls threshold = 0.
+In order for a feature center to be determined the range of pixel intensities
+around the feature must exceed this threshold.
+.le
+.ls minsep = 2.
+The minimum separation, in pixels, allowed between feature positions
+when defining a new feature.
+.le
+
+The following parameters control the input and output.
+.ls logfile = "logfile"
+Log file for recording the results of the velocity measurements.  The
+results are written when exiting or changing input images.  The
+results can be previewed with the ":features" command.  If no log file
+is specified then the results are not saved.
+.le
+.ls autowrite = no
+Automatically write or update the logfile and database?  If no then a query
+is given for writing results to the logfile.  A query for writing to the
+database is also given if the feature data have been modified.  If yes
+exiting the program automatically writes to the logfile and updates the
+database.
+.le
+.ls keywpars = ""
+The image header keyword translation table as described in 
+the \fIkeywpars\fR named pset.  This defines the header keywords used
+to obtain the observation information needed for computing the
+heliocentric velocity.
+.le
+.ls graphics = "stdgraph"
+Graphics device.  The default is the standard graphics device which is
+generally a graphics terminal.
+.le
+.ls cursor = ""
+Cursor input file.  If a cursor file is not given then the standard graphics
+cursor is read.
+.le
+.ih
+ADDTIONAL PARAMETERS
+The measured velocities are corrected to a heliocentric frame of reference
+if possible.  This requires determining various parameters about the
+observation.  The latitude, longitude, and altitude of the observation
+are determined from the observatory database.  The observatory is
+defined by either the OBSERVAT image header keyword or the "observatory"
+package parameter in that order.  See the help for \fBobservatory\fR
+for additional information.
+
+The date, universal time, right ascension, declination, and coordinate epoch
+for the observation are obtained from the image header.  The keywords
+for these parameters are defined in the \fBkeywpars\fR parameter set.
+Note that the parameters used are "ra", "dec", "ut", and "date-obs".
+The "utmiddle" parameter is not used so if you have a keyword for the
+middle of the exposure that you want to use then you must set the
+"ut" parameter to reference that keyword.
+
+Before IRAF V2.12, if the date keyword included a time then that time was
+used and the "ut" keyword was not used.  In V2.12 this was changed and the
+time is always taken from the keyword specified by "ut".  However, the
+value can be in either a single time or a date/time string.  So if you
+want to use both the date and time from the same keyword, say DATE-OBS,
+then point the "date_obs" and "ut" parameters in KEYWPARS to the same
+keyword.
+.ih
+CURSOR KEYS
+
+.nf
+?  Clear the screen and print menu of options
+a  Apply next (c)enter or (d)elete operation to (a)ll features
+b  Mark and de(b)lend features by Gaussian fitting
+c  (C)enter the feature nearest the cursor
+d  (D)elete the  feature nearest the cursor
+f  (F)it redshift and velocity from the fitted and user coordinates
+i  (I)nitialize (delete features and coordinate fit)
+j  Go to the preceding image line/column/band/aperture
+k  Go to the next image line/column/band/aperture
+l  Match coordinates in the coordinate (l)ist
+m  (M)ark new feature near the cursor and enter coord and label
+n  Move the cursor or zoom to the (n)ext feature (same as +)
+o  Go to the specified image line/column/band/aperture
+p  (P)an to user defined window after (z)ooming on a feature
+q  (Q)uit and continue with next image (also carriage return)
+r  (R)edraw the graph
+t  Reset the position of a feature without centering
+u  Enter a new (u)ser coordinate and label for the current feature
+w  (W)indow the graph.  Use '?' to window prompt for more help.
+y  Automatically find strongest peaks and identify them
+z  (Z)oom on the feature nearest the cursor
+.  Move the cursor or zoom to the feature nearest the cursor
++  Move the cursor or zoom to the next feature
+-  Move the cursor or zoom to the previous feature
+I  Interrupt task and exit immediately
+.fi
+
+The parameters are listed or set with the following commands which may be
+abbreviated.  To list the value of a parameter type the command alone.
+
+.nf
+:show file		Show the values of all the parameters
+:features file		Write feature list to file (default STDOUT)
+
+:coordlist file		Coordinate list file
+:cradius value		Centering radius in pixels
+:threshold value	Detection threshold for feature centering
+:database name		Database for recording feature records
+:ftype value		Feature type
+			  (emission|absorption|gemission|gabsorption)
+:fwidth value		Feature width in pixels
+:image imagename 	Set a new image or show the current image
+:labels value		Feature label type
+			    (none|index|pixel|coords|user|both)
+:match value		Coordinate list matching distance
+:maxfeatures value	Maximum number of features automatically found
+:minsep value		Minimum separation allowed between features
+:read name ap		Read a record from the database
+			  (name/ap default to the current spectrum)
+:write name ap		Write a record to the database
+			  (name/ap default to the current spectrum)
+:add name ap		Add features from the database
+			  (name/ap default to the current spectrum)
+:zwidth value		Zoom width in user units
+
+Labels:
+      none - No labels
+     index - Sequential numbers in increasing pixel position
+     pixel - Pixel coordinates
+    coords - User coordinates such as wavelength
+      user - User labels
+      both - Combination of coords and user
+.fi
+.ih
+DESCRIPTION
+\fBRvidlines\fR measures radial velocities from spectra by determining the
+wavelength shift in spectral lines relative to specified rest wavelengths.
+The basic usage consists of identifying one or more spectral lines (also
+called features), entering the rest wavelengths, and computing the average
+wavelength shift converted to a radial velocity.  Additional lines can then
+be automatically added from a coordinate list of rest wavelengths.
+
+Each dispersion calibrated image in the input list is examined in turn.  If
+the image is not one dimensional or a one dimensional section of an image
+then the image section given by the parameter \fIsection\fR is used.  This
+parameter may be specified in several ways as described in the parameter
+and examples sections.  The image section is used to select a starting
+vector and image axis.  The parameter \fInsum\fR determines the number
+of lines, columns, or bands to sum in a two or three dimensional image.
+
+Once a spectrum has been selected it is graphed.  The graph title includes
+the image name, spectrum title, and the current velocity and redshift if
+one has been determined.  An initial feature list is read from the database
+if an entry exists.  The features are marked on the graph by tick marks.
+The features may also be labeled using the ":label" option.  The graph has
+the observed wavelength scale along the bottom and the rest wavelength
+scale along the top (if a velocity has been determined).  The status line
+gives the pixel coordinate, observed wavelength, rest wavelength (as
+computed by the last velocity computation), the true rest wavelength, the
+velocity residual, and an optional identification string for the "current"
+feature.
+
+The graphics cursor is used to select features and perform various
+functions.  A menu of the keystroke options and functions is printed with
+the key '?'.  The cursor keys and their functions are defined in the CURSOR
+KEYS section and described further below.  The standard cursor mode keys
+are also available to window and redraw the graph and to produce hardcopy
+"snaps".
+
+There are two types of feature selection functions;  defining new
+features and selecting previously defined features.  The 'm' key marks
+a new feature near the cursor position.  The feature position is
+determined by a centering algorithm.  There are two algorithms;
+a flux bisecting algorithm called \fBcenter1d\fR and a gaussian
+profile fitting algorithm.  The choice of fitting algorithm and whether the
+feature is an emission or absorption line is set by the \fIftype\fR
+parameter.
+
+The center1d algorithm is described in the help topic \fBcenter1d\fR.  The
+parameters which control it are \fIfwidth\fR, \fIftype\fR, \fIcradius\fR,
+and \fIthreshold\fR.
+
+The gaussian fitting algorithm estimates a linear local background by
+looking for the minimum or maximum, depending on whether the feature type
+is set to absorption or emission, within a distance of the entered cursor
+position of one-half the feature width specified by the \fIfwidth\fR
+parameter plus the centering error radius specified by the \fIcradius\fR
+parameters.  This background estimation is crude but generally is not
+critical for reasonably strong lines.  Once the sloped background is
+defined a non-linear Levenberg-Marquardt algorithm determines the gaussian
+center, peak strength, and sigma.  The initial estimates for these
+parameters are the starting center, the background subtracted pixel value
+at the starting center, and the \fIfwidth\fR value divided by six.  After
+fitting the gaussian model it is overplotted on the data for comparison.  The
+\fIthreshold\fR parameter also applies to this algorithm to check for a
+minimum data range and the \fIcradius\fR parameter checks for a maximum
+error in the center from the initial value.
+
+For a more critical setting of the background in the gaussian algorithm or
+for the simultaneous solution of multiple gaussian components (deblending)
+the 'b' key is available.  The 'b' key is used to mark the initial
+positions of up to ten features.  The feature marking ends with 'q'.  The
+user is then queried to mark two points for the linear background.  After
+doing the simultaneous fitting the user is queried sequentially for the
+rest wavelengths of each line.  Note that the 'b' key will do the gaussian
+fitting regardless of whether the \fIftype\fR setting is for a gaussian
+or not and can be used for fitting just a single line.
+
+When a feature is defined the value of \fIftype\fR and \fIfwidth\fR are
+associated with the feature.  Subsequent recentering will use these values
+even if the default values are changed.  This is how a combination of
+absorption and emission lines may be defined.  The only constraint to this
+is that the feature data does not record the combination of lines used in a
+deblending operation so automatic recentering will treat each line
+separately.
+
+When a new feature is marked if the wavelength is within a distance given
+by the parameter \fIminsep\fR of a previous feature it is considered to be
+the same feature and replaces the old feature.  The coordinate list is
+searched for a match between the measured wavelength, corrected to rest
+using the current velocity, and a user coordinate in the list.  The
+matching is based on the nearest line within a specified \fImatch\fR
+distance.  If a match is found it becomes the default user coordinate which
+the user may override.  The new feature is marked on the graph and it
+becomes the current feature.  The redefinition of a feature which is within
+the minimum separation may be used to set the user coordinate from the
+coordinate list.  The 't' key allows setting the position of a feature to
+other than that found by the centering algorithms.
+
+If at least one feature is marked with it's rest wavelength specified then
+the 'l' key may be used to identify additional features from a coordinate
+list of rest wavelengths.  First a velocity is computed from the initial
+features.  Then each coordinate in the list is corrected to the
+observed velocity and a feature is sought in the data at that point.
+Up to a maximum number of features, set by the parameter \fImaxfeatures\fR,
+may be defined in this way.  A new velocity is computed using all the
+located features.
+
+The 'y' key provides another way to add features.  Rather than look for
+features at the coordinates of a list, a peak finding algorithm is used to
+find features up to the specified maximum number.  If there are more
+peaks only the strongest are kept.  The peaks are then matched against the
+coordinate list to find user coordinate values.
+
+To select a different feature as the current feature the keys '.', 'n',
+'+', and '-' are used.  The '.' selects the feature nearest the cursor, the
+'n' and '+' select the next feature, and the '-' selects the previous
+feature relative to the current feature in the feature list as ordered by
+pixel coordinate.  These keys are useful when redefining the user
+coordinate with the 'u' key and when examining features in zoom mode.
+
+The key 'f' computes ("fits") a velocity to the defined features.
+This is done by taking a weighted average of the redshifts,
+
+.nf
+	z = (measured - true) / true
+.fi
+
+of the individual lines.  The default weights are always one but a different
+weight may be entered with the 'u' key.  The average redshift is
+converted to a Cz velocity (redshift times the speed of light) and
+corrected to a heliocentric frame if possible.
+
+The heliocentric correction requires observatory and observation information.
+The observatory is determined either from the OBSERVAT keyword in the
+image header or by the "rv.observatory" package parameter.  For a
+discussion of how an observatory is defined and used see the help
+for \fBobservatory\fR.  In addition to the observatory the right
+ascension, declination, coordinate epoch, and date and time of the
+observation are required.  If the time is in the date string it has
+precedence over the time keyword.  This information is sought in the image
+header using the keywords defined in the \fBkeywpars\fR parameter
+file.  If there is insufficient information for the heliocentric
+velocity correction only the observed velocity will be given.  The
+type of velocity (both velocity and redshift) is indicated by
+identifiers such as Vobs and Vhelio.
+
+Note that a new velocity is only computed after typing 'f', 'l',
+":features", or when exiting and writing the results to the database.
+In other words, adding new features or deleting existing features
+does not automatically update the velocity determination.
+
+Features may be deleted with the key 'd'.  All features are deleted
+when the 'a' key immediately precedes the delete key.  Deleting the
+features does not reset the velocity.  The 'i' key initializes
+everything by removing all features and reseting the velocity.
+
+It is common to transfer the feature identifications and velocities
+from one image to another.  When a new image without a database entry
+is examined, such as when going to the next image in the input list,
+changing image lines or columns with 'j', 'k' and 'o', or selecting
+a new image with the ":image" command, the current feature list and
+velocity are kept.  Alternatively, a database record from a different
+image may be read with the ":read" command.  When transferring feature
+identifications between images the feature coordinates will not agree exactly
+with the new image feature positions and several options are available to
+reregister the feature positions.  The key 'c' centers the feature nearest
+the cursor using the current position as the starting point.  When preceded
+with the 'a' key all the features are recentered (the user must refit
+the coordinate function if desired).  As an aside, the recentering
+function is also useful when the parameters governing the feature
+centering algorithm are changed.  An additional options is the ":add"
+command to add features from a database record.  This does not overwrite
+previous features as does ":read".
+
+Note that when a set of spectra all have the same features in nearly
+the same location the task \fBrvreidlines\fR may be used to reidentify
+the lines and compute a new velocity.
+
+In addition to the single keystroke commands there are commands initiated
+by the key ':' (colon commands).  As with the keystroke commands there are
+a number of standard graphics features available beginning with ":." (type
+":.help" for these commands).  The rvidlines colon commands allow the task
+parameter values to be listed and to be reset within the task.  A parameter
+is listed by typing its name.  The colon command ":show" lists all the
+parameters.  A parameter value is reset by typing the parameter name
+followed by the new value; for example ":match 10".  Other colon commands
+display the feature list and velocities (:features), control reading and
+writing records to the database (:read and :write), and set the graph
+display format.
+
+The feature identification process for an image is completed by typing 'q'
+to quit.  Attempting to quit an image without explicitly logging the
+results or recording changes in the feature database produces a warning
+message unless the \fIautowrite\fR parameter is set.  If this parameter is
+not set prompts are given asking whether to save the results to the log
+file and the database, otherwise the results are automatically saved.  As
+an immediate exit the 'I' interrupt key may be used.  This does not save
+the feature information and may leave the graphics in a confused state.
+
+The information recorded in the logfile, if one is specified, includes
+information about the observatory used for heliocentric corrections
+(to verify the correct observatory was used), the list of features
+used in the velocity computation, the wavelength and velocity RMS,
+and lines with the observed and heliocentric redshifts and velocities.
+These lines include an error in the mean derived from the weighted
+RMS and the number of lines used, and the number of lines.  This output
+format is designed so that if there are multiple velocities recorded
+in the same log file they can be easily extracted with the match command:
+
+.nf
+    cl> match Vhelio logfile
+    im1 45 : Vhelio = 15.06 km/s, Mean err = 4.593 km/s, Lines = 7
+    im1 40 : Vhelio = 17.77 km/s, Mean err = 3.565 km/s, Lines = 7
+    im2 45 : Vhelio = 24.44 km/s, Mean err = 3.741 km/s, Lines = 7
+    im2 40 : Vhelio = 14.65 km/s, Mean err =  11.2 km/s, Lines = 7
+    ...
+.fi
+.ih
+DATABASE RECORDS
+The database specified by the parameter \fIdatabase\fR is a directory of
+simple text files.  The text files have names beginning with 'id' followed
+by the entry name, usually the name of the image.  The database text files
+consist of a number of records.  A record begins with a line starting with the
+keyword "begin".  The rest of the line is the record identifier.  Records
+read and written by \fBrvidlines\fR have "identify" as the first word of the
+identifier.  Following this is a name which may be specified following the
+":read" or ":write" commands.  If no name is specified then the image name
+is used.  For 1D spectra the database entry includes the aperture number
+and so to read a solution from a aperture different than the current image
+and aperture number must be specified.  For 2D/3D images the entry name
+has the 1D image section which is what is specified to read the entry.
+The lines following the record identifier contain
+the feature information and redshift (without heliocentric correction).
+
+The database files have the name "identify" and the prefix "id" because
+these files may also be read by the \fBidentify\fR task for changing
+the dispersion function based on the rest wavelengths.
+.ih
+EXAMPLES
+1.  The radial velocity of the  spectrum, kstar1, is to be determined.
+The user creates a list of line features to be used in the file
+klines.dat.
+
+.nf
+    cl> rvidlines kstar1 coord=klines.dat
+	a. The spectrum is drawn
+	b. A line is marked with 'm'
+	c. Enter the rest wavelength
+	d. Compute a velocity with 'f'
+	e. Find other lines in the list with 'l'
+	f. Exit with 'q'
+    Write velocity data to the logfile (yes)? y
+    Write feature data to the database (yes)? y
+    cl> match Vhelio logfile
+    kstar1 1 : Vhelio = 25.1 km/s, Mean err = 1.123 km/s, Lines = 10
+.fi
+
+2.  For echelle or multispec spectra the keys 'o', 'j', and 'k' may
+be used to switch between spectra.  Note that the inheritance of features
+in echelle orders is not very useful.  So the 'i' can be used to
+initialize.  For similar spectra the 'a''c' key combination may
+be used to recenter all lines and the a new 'f' fit can be done.
+
+3.  For images which are two or three dimensional it is necessary to
+specify the image axis for the data vector and the number of pixels at each
+point across the vector direction to sum.  One way specify a vector is to
+use an image section to define a vector.  For example, to select column
+20:
+
+.nf
+    cl> rvidlines obj[20,*]
+.fi
+
+The alternative is to use the section parameter.  Below are some examples
+of the section parameter syntax for an image "im2d" which is 100x200
+and "im3d" which is 100x200x50.  On the left is the section string syntax
+and on the right is the image section
+
+.nf
+    Section parameter |  Image section      |  Description
+    ------------------|---------------------|---------------------
+    first line        |  im2d[*,1]          |  First image line
+    middle column     |  im2d[50,*]         |  Middle image column
+    last z            |  im3d[100,200,*]    |  Last image z vector
+    middle last y     |  im3d[50,*,50]      |  Image y vector
+    line 20           |  im2d[*,20]         |  Line 20
+    column 20         |  im2d[20,*]         |  Column 20
+    x 20              |  im2d[*,20]         |  Line 20
+    y 20              |  im2d[20,*]         |  Column 20
+    y 20 30           |  im2d[20,*,30]      |  Column 20
+    z 20 30	      |  im3d[20,30,*]      |  Image z vector
+    x middle          |  im3d[*,100,25]     |  Middle of image
+    y middle          |  im3d[50,*,25]      |  Middle of image
+    z middle          |  im3d[50,100,*]     |  Middle of image
+.fi
+
+The most common usage should be "middle line", "middle column" or "middle z".
+
+The summing factors apply to the axes across the specified vector.  For
+3D images there may be one or two values.  The following shows which axes
+are summed, the second and third columns, when the vector axis is that shown
+in the first column.
+
+.nf
+    Vector axis       |   Sum axis in 2D    |  Sum axes in 3D
+    ------------------|---------------------|--------------------
+         1            |         2           |      2 3                 
+         2            |         1           |      1 3                 
+         3            |         -           |      1 2                 
+.fi
+
+.ih
+REVISIONS
+.ls RVIDLINES V2.11
+This task will now work in the units of the input spectra.
+.le
+.ls RVIDLINES V2.10.3
+This is a new task in this version. 
+.le
+.ih
+SEE ALSO
+center1d, fxcor, gtools, identify, keywpars, observatory,
+rvcorrect, rvreidlines
+.endhelp
diff --git a/noao/rv/doc/rvpackage.spc b/noao/rv/doc/rvpackage.spc
new file mode 100644
index 00000000..216f622b
--- /dev/null
+++ b/noao/rv/doc/rvpackage.spc
@@ -0,0 +1,948 @@
+.EQ
+delim $$
+.EN
+.RP
+.TL
+Specifications for the Radial Velocity Analysis Package
+
+.AU
+Michael J. Fitzpatrick
+.AI
+.K2 "" "" "*"
+Revised January 1990
+
+.AB
+.PP
+Specifications are presented for an IRAF package to compute radial velocity,
+redshift and dispersion information from both one and two dimensional
+IRAF images.  Requirements and specifications for each necessary task are
+described as well as the algorithms used.  Specifications of user input
+and program output are also discussed.  Detailed manual pages of the tasks
+are included following this document.
+.AE
+
+.NH
+Introduction
+.PP
+The following document describes the specifications for the radial velocity
+package.  This package will be designed to produce radial velocity, redshift
+and dispersion data for both one and two dimensional images.  To this end
+both cross correlation and Fourier techniques will be employed, thus allowing
+the user to choose the method of correlation best suited to his data.  Since
+the needs of the individual astronomer will differ,  the tasks in this package
+will use different algorithms for computation but will share some common
+output.  This common output may later be used to compare the results of one
+method over another, or one parameter set over another.
+.PP
+Most radial velocity work is done by cross correlating a standard template star
+with an unknown object spectrum.  This is most often the case with a one 
+dimensional data set in which the value of interest is the heliocentric radial
+velocity of the object star measured with respect to the template star 
+(which is usually a radial velocity standard of known velocity).  Several
+ methods will be used to provide this information:
+.IP \(bu 
+A standard Fourier correlation technique in which the data are transformed 
+and then mulitplied one by the complex conjugate of the other and reverse
+transformed, thus procuding a normalized cross correlation function.
+Filtering of the data while in Fourier space is allowed.  Error calculations
+are also better prepared because of the nature of the algorithms.
+.IP \(bu
+A squared difference method in which the sums of the squared difference between
+the intensities of the two spectra are computed at each trial shift. This 
+produces an unnormalized function which may be used to compute a relative 
+shift and hence velocity.  Restictions on this task will be rather loose
+to allow it to be used more efficiently as a "quick-look" device.
+.IP \(bu
+A direct correlation method, identical in operation to the squared difference
+task yet producing a normalized correlation function.
+.LP
+All of the resulting functions are fit with a user specified function 
+providing a more accurate velocity.  The details of these functions and 
+relative merits of the methods are discussed below.
+.PP
+A second desire of astronomers using this package is to correlate a galaxy 
+spectrum against a standard template spectrum.  While this may be done with
+one dimensional data to produce a redshift value, it is often used with
+two dimensional data in which the aim is produce a velocity dispersion of the
+galaxy with respect to a distance \fIr\fR from the center.  Using this 
+information at different position angles across the galaxy image, it is
+possible to map a velocity field 
+within the galaxy, describing it's rotation. Again, two methods will be used
+to provide this information.
+.IP \(bu
+A Fourier quotient method in which the ratio of the Fourier transforms of 
+the galaxy to the stellar spectra are fit to the Fourier transform of a chosen 
+broadening function, the results of which provide the velocity dispersion,
+redshift, and relative line strength parameter.
+.IP \(bu
+A Fourier difference method in which the difference of the Fourier transforms 
+of the galaxy and star spectra are fit to the Fourier transform of a chosen 
+broadening function, the results of which provide the velocity dispersion,
+redshift, and relative line strength parameter.
+.LP
+The details of these functions and methods and their relative merits 
+are discussed below.
+.PP
+Each of the tasks in this package will also act as an interactive parameter
+editor, permitting the user to change task parameter values and immediately
+examine the effect on the data.  The user may then save these parameters for
+a batch (non-interactive) run or process each of the images individually.
+.PP
+Although it will be generally assumed that the data have been prepared using
+other applications available within IRAF, a limited set of data preparation
+commands will be available within each of the major tasks.  (A more in depth
+description of these tasks is found below.) These commands will perform the 
+following functions:
+.IP \(bu
+Filtering of the data while in Fourier space.  Often times it may be necessary
+to filter certain frequency components from the data that may artificially
+weight the correlation.  A choice of filter functions will be available and
+the user may specify the fourier components over which the filter will operate.
+.IP \(bu 
+Removal of a local continuum.  While this task is easily accomplished with
+either the \fICONTINUUM\fR task or selective filtering, it is sometimes
+desireable to remove a continuum from the data at this step of the analysis.
+The user specifies the order of a polynomial or spline to be fit to the 
+data to remove low frequency trends in the data.  This fitted function may be
+either subtracted or divided from the data.
+.IP \(bu
+Masking of regions to be used in the correlation.  To exclude sparse 
+line regions,
+bad pixels, or telluric features, it will sometimes be necessary to input a
+specific region to be used in the correlation.  The user is able to specify in
+either pixel number or wavelength the regions to be included in the 
+correlation.  Since a broad error in the chip or wide feature may weight the
+continuum fitting, continuum fitting will also take advantage of regions via
+the \fICONTINUUM.SAMPLES\fR parameter.
+
+.NH
+Input Requirements and Specifications
+.PP
+The following requirements and specifications will be met with regard
+to input format to all of the tasks:
+.IP \(bu
+The object and template stars may both be specified as lists.  Both lists
+may be positioned forward and backward from interactive operation with a colon
+command. In interactive mode the user is required to position each list
+separately. In batch mode each object spectrum is correlated to each 
+template in the list before moving on to the next object.
+.IP \(bu
+The user may specify an aperture list to be used in the correlation.  
+This aperture list will be used in both the object and template spectrum.
+It may be used to specify an echelle order or simply the row number in
+a two dimensional image to be used if for some reason data have been stacked.
+In the case of a two dimensional object/template spectrum and it's one
+dimensional counterpart, the aperture number will apply only to the two
+dimensional data.
+.IP \(bu
+The new IRAF echelle and multispec formats will be supported.
+.IP \(bu
+Data are required to be binned linearly in logarithm of the wavelength for 
+Fourier tasks.  The squared difference or direct correlation
+task may use either log-wavelength,
+wavelength, or pixel scaled data. For pixel scaled data, output will
+contain only pixel shift information since velocity information cannot be 
+computed. Data may be rebinned automaticall with the appropriate task through
+use of the \fIPROCESSPARS\fR pset (see below).
+.KS
+.IP \(bu
+The following information must be contained in each object image header in
+order for the heliocentric correction to be done properly:
+.nf
+.ta 1i 2i 3i
+	ra	- Right Ascension of object
+	dec	- Declination of object
+	date-obs	- UT Date of observation
+	ut	- UT time of observation
+	epoch	- Epoch of observation
+	exptime/otime	- Exposure time of frame
+	w0/crval1	- Starting wavelength in Angstroms or log(Angstroms)
+	wpc/crdelt1	- Wavelength increment in Angstroms or log(Angstroms)
+.fi
+Keyword translation is handled by the \fIRVKEYWORDS\fR pset as discussed
+below.  Warning messages will be issued for missing keywords, which may
+affect the accuracy of the results.
+.KE
+.IP \(bu
+The user may input a number of rows that will be averaged according to
+user specifications to be used in the correlation for the \fIXCOR2D\fR
+task.  For two dimensional data it may be desired to average a number of 
+rows into bins for computation rather than doing each row independantly.  
+Presently the template spectrum is assumed to be a one dimensional spectrum,
+if not only the first row will be used in the correlation.
+.IP \(bu
+The \fIMKBINS\fR task may be used to create bins of approximately equal 
+intensity.  A description of this task and the database structure used 
+is described below.
+
+.NH 2 
+Rebinning of Input Data
+.PP
+Input data should be dispersion corrected, and while certain tasks require that
+the data be presented on a logarithmic scale, it shall be possible to input
+data which are not logarithmically binned.  In this case, and if required by the
+task, the data shall be rebinned automatically from the data I/O routines using
+the same (or equivalent) starting wavelength and wavelength per channel values.
+An informational message will be enetered into the log file indicating that 
+the data have been rebinned.
+.PP
+The parameters controlling data rebinning will be retrieved from 
+the \fIprocesspars\fR pset and the image header.  The interpolation function 
+may be changed with the \fI:rb_func [s_value]\fR command followed by 
+a \fI:rebin\fR command to perform the action.  This ability will be common to 
+all tasks.  When data have been rebinned, a note will be made to the log file.
+In batch operation of any task, the data will be rebinned automatically if
+required and the appropriate notes made to the log file.
+.PP
+The \fIw0\fR, \fIwpc\fR and \fInpts\fR parameters will be obtained from the
+current image header in the \fIprocesspars\fR value is INDEF, otherwise these
+may be set to overide the current value.
+.PP
+If the user is not satisfied with rebinning the data using the current 
+dispersion or number of points, the \fIdo_rebin\fR parameter should be turned
+off and the data rebinned outside the task using one of the other available
+tasks.  If \fIdo_rebin\fR is disabled and data must be rebinned, the task
+will abort with an error message.
+.NH 2
+Continuum Removal From the Data
+.PP
+It shall be possible for the user to continuum normalize the data in a manner
+identical to that done by the \fIonedspec.continuum\fR task.  The data
+input to the Fourier tasks should be normalized by subtracting the continuum
+and dividing by the average to get a mean of zero with excursions of order
+unity.  The \fIrvfquot\fR and \fIrvfdiff\fR tasks need to know the value of the
+spectrum average in order to compute the photon counting statustucs before 
+normalization so it is advised that continuum 
+normalization be left to the task (i.e. use the normalization commands
+available in the tasks as opposed to the \fIcontinuum\fR task)
+The apodized, normalized spectrum may be previewed by issuing a \fI:cont\fR 
+command to do the normalization and a \fIn\fR keystroke to show a split-plot 
+of the flattened data
+.PP
+Interactive flattening of the data behaves exactly like the \fIcontinuum\fR
+task, except that the data are divided by the average once the continuum has
+been subtracted.  If the \fIprocesspars.type\fR parameter is set to "ratio"
+then the data will be normalized to a mean of unity and will not be divided
+by the average.
+
+.NH
+Output Requirements and Specifications
+.PP
+Output from the tasks will take the form of either graphics drawn to the
+standard graphics device, metacode to a graphics spool file, or text 
+(sometimes verbose) output to a spool file and the screen (the abridged 
+version).  With the exception of the pset tasks, all other tasks in this 
+package may have graphics and or text output.
+.NH 2 
+Graphics Output
+.NH 3
+Graphics Metacode
+.PP
+The simplest graphical output from the tasks \fIrvfquot\fR and \fIrvfdiff\fR,
+will be metacode for the quotient or difference plots (if the \fIfit_plot\fR
+or \fIdiff_plot\fR parameters are set) and the FFT's of the data (if 
+the \fIfft_plot\fR parameter is set).
+The simplest graphical output from the tasks \fIrvsqdiff\fR and \fIrvxcor\fR 
+gin
+
+will be metacode of the correlation plot and it's fitted function (s) directed 
+to a user named spool file.  
+.PP
+Metacode from the \fIrvdisp\fR task will be written to a user defined file
+and consist only of the computed dispersion curves and fit.
+.PP
+These plots may later be viewed with the \fIgkimosaic\fR task to quickly view 
+the results of a batch process.  Each time the user uses either the 'g' or 'y'
+commands to fit to new points, metacode for the new fit will also be written.
+.NH 3
+Standard Graphics Plots
+.PP
+Plots drawn to the screen from the four main cross correlation tasks will 
+consist of the following:
+.IP \(bu
+An overplot of the two spectra upon task startup and every time a new image
+is read (except when the \fIspec_plot\fR parameter is set).  The mean of the
+data will be normalized to unity to allow for the overplotting of the two
+spectra, which may be at different intensity scales.  The mean is used instead
+of the maximum so that cosmic ray events will not affect the plotting.
+.IP \(bu
+A plot of the Fourier transform of each spectrum to aide the user in choosing
+a proper filter.  This plot will be generated for each spectrum's transform
+and shown to the user by typing the 'f' command.  After viewing the plots
+the user may issue commands to select an appropriate filter.
+.IP \(bu
+A graph of the fitting function.  The fitted function will be overplot on the
+correlation function once the endpoints have been selected and the fit 
+completed.  This plot is also written to the metacode file if specified.
+.IP \(bu
+For the tasks \fIrvxcor\fR and \fIrvsqdiff\fR a correlation plot produced
+by those methods. This plot is also written to the metacode file if specified.
+.IP \(bu
+For the \fIrvfquot\fR task a plot of the ratio of the galaxy to stellar 
+spectrum projected onto a unit vector $exp(-2 pi i k zeta / n)$ where $zeta$
+is the logarithmic redshift.  For two dimensional galaxy spectra, 
+each bin will produce a quotient plot if the \fIquot_plot\fR parameter 
+is set.
+.IP \(bu
+For the \fIrvfdiff\fR task a plot of the difference of the galaxy and stellar 
+spectrum.  For two dimensional galaxy spectra, 
+each bin will produce a difference plot if the \fIdiff_plot\fR parameter 
+is set or a summary plot if the \fIsummary_plot\fR parameter is set.
+.NH 2
+Text Output
+.PP
+Text output to the logfile common to each task will be the following:
+.IP \(bu
+An optional header explaining the meaning of each parameter if the \fIheader\fR
+parameter is set.
+.IP \(bu
+The initial parameters of the reduction, one to a line consisting of a 
+'#P' in the first two columns identifying the line as a parameter, the
+parameter name, and it's value.  Each time a parameter is changed from the
+command loop, a new line will be written to the log file showing the new
+value of the parameter.
+.IP \(bu
+A keyword formatted the same as the parameter line identifying the
+image name (IMAGE), the object name (OBJECT), the template image
+name (TEMPLATE), the bin number used (BIN_NO), the correlation or
+reduction method (CORM) and the fitting function used (FITF).
+.IP \(bu
+A date/time string identifying the date/time of reduction.
+.IP \(bu
+Any error or warning messages issued from the task.
+.IP \(bu
+A data record containing values input to or computed by the task.
+For the \fIrvxcor\fR and \fIrvsqdiff\fR tasks, the data record will 
+contain:
+.RS
+.IP \(bu
+Heliocentric Julian Date
+.IP \(bu
+Computed pixel shift and error of fit to CCF
+.IP \(bu
+FWHM of CCF peak in pixels
+.IP \(bu
+Height of the peak
+.IP \(bu
+Observed radial velocity
+.IP \(bu
+Heliocentric radial velocity
+.IP \(bu
+The derived velocity dispersion.
+.IP \(bu
+Comments of reduction, identifying errors or trouble spots.
+.RE
+For the \fIrvfquot\fR and \fIrvfdiff\fR tasks, the data record will 
+contain:
+.RS
+.IP \(bu
+Heliocentric Julian Date
+.IP \(bu
+Observed redshift, line strength parameter and dispersion
+.IP \(bu
+Heliocentric redshift
+.IP \(bu
+Error of fit to difference or quotient
+.IP \(bu
+Comments of reduction, identifying errors or trouble spots.
+.RE
+.NH 2
+Database Records
+.PP
+Dispersion calculations require that the solution from fitting the
+dispersion curve (i.e. a curve produced by convolving Gaussians
+of known width with stellar spectra and comparing the input gaussian
+width with the derived correlation peak width) be used by the \fIrvxcor\fR
+and \fIrvsqdiff\fR tasks to convert the derived correlation peak widths
+to true dispersions.  Since this is usually done empirically, the 
+task \fIrvdisp\fR will be used to convolve a stellar spectrum with
+user specified widths and fit the resulting curve with a polynomial 
+of order $n$.  The parameters used to create this curve as well as the
+coefficients of the polynomial will be written in the form of a database
+record.  
+.PP
+The name of the database file may then be passed to either the \fIrvxcor\fR
+or \fIrvsqdiff\fR tasks which will use the coefficients to convert
+the correlation widths.  The correlation tasks will also check each
+record in a file to find one in which the parameters used for the
+dispersion curve calculation match those used for the correlation.
+Failing a match of parameters, no dispersion calculation will be done, however
+a velocity value of the FWHM width will be printed.
+Changing parameters in a task will also force a search search for a new 
+record to match the parameters.
+.PP
+Below is an example database record used by the \fIrvdisp\fR, \fIrvxcor\fR 
+and \fIrvsqdiff\fR tasks.
+.nf
+
+	#T  Aug 31 14:50 
+	begin
+	    image		star001
+	    object		HR1762
+	    corrfunc		fourier
+	    fitfunc		parabola
+	    filterpars
+	        filter 		yes
+	        filtertype	hanning
+	        cuton		5
+	        cutoff		150
+	        fullon		0
+	        fulloff		0
+	    apodize		0.1
+	    order		4
+	    vstart		10.0
+	    vincrement		5.0
+	    npts		10
+	    coeffs		4
+		0.21345 
+		0.82548 
+		0.02345 
+		0.00342
+.fi
+
+.NH
+Interactive Parameter Editing
+.PP
+One common trait of all the tasks is the ability to change
+the value of parameters interactively using colon commands.  The user
+is able to evaluate the result of each parameter change and then decide
+on the best value for his reduction.  The basic idea is to allow the user to
+examine the effects of different parameter values on a typical set of
+data and then process the input list with the chosen parameters.  The other
+envisioned use is of an astronomer that has completely different data and
+wishes to reduce each star individually.
+.PP
+One other point that should be noted is the interaction of parameters between
+tasks in the package.  For instance, the filtering parameters set by 
+the \fIfilterpars\fR pset are used by the \fIrvdisp\fR, \fIrvxcor\fR
+and \fIrvsqdiff\fR tasks.  Similarly, parameters used in the \fIrvdisp\fR
+task should match as closely as possible those used in the correlation
+tasks since the computation of the dispersion value relies on the fit
+to the dispersion curve (which may or may not be the same for different
+parameters).  For this reason, many of the colon commands will be the 
+same between different tasks. 
+.PP
+The \fI':update'\fR command is provided to save the chosen parameters to the 
+task or pset parameter files.   
+This command will also update the \fIfilterpars\fR
+pset if given an argument of 'filter' (likewise for the other package psets).  
+Similarly, the \fI':unlearn'\fR command is provided to 
+reset the parameters to their default values.  It should, however, be used
+with care and as a last resort to reset the parameters to their defaults. 
+Each time a parameter is changed which will affect the output, a note is made 
+in the spool file reflecting the new parameter value.
+
+.br
+.NH 
+Use of Parameter Sets in the Package
+.PP
+.NH 2
+Image Header Keyword Translation
+.PP
+The following parameters control translation of image header keywords.  If
+the exposure time for the frame is given by the "EXPTIME" keyword in your
+image header, as opposed to the "OTIME" keyword, just change the value of
+the keyword.
+.nf
+
+	(ra = "RA")				Right Ascension keyword
+	(dec = "DEC")			Declination keyword
+	(ut = "UT")				UT of observation keyword
+	(exptime = "OTIME")		Exposure time keyword
+	(epoch = "EPOCH")		Epoch of observation keyword
+	(date_obs = "DATE-OBS")	Date of observation keyword
+	(w0 = "W0")			Starting wavelength keyword
+	(wpc = "WPC")			Wavelength per channel keyword\n
+	(hjd = "HJD")			Heliocentric Julian date
+	(vobs = "VOBS")			Observed velocity keyword
+	(vhelio = "VHELIO")		Heliocentric velocity keyword
+	(vlsr = "VLSR")			LSR velocity keyword
+.fi
+.NH 2 
+Processing Parameters
+.PP
+The following parameters control operation of the continuum removal and
+data rebinning. INDEF values in the rebinning parameters indicate that
+those values should be obtained from the image header.
+.nf
+	(do_cont = yes)			Do continuum normalization?
+	(interactive = no)			Fit continuum interactively?
+	(type = "difference")		Type of output (diff|ratio)
+	(sample = "*")			Sample of points to use in fit
+	(naverage = 1)			Number of points in sample averaging
+	(function = "spline3")		Fitting function
+	(order = 1)				Order of fitting function
+	(low_reject = 2.)			Low rejection in sigma of fit
+	(high_reject = 2.)			High rejection in sigma of fit
+	(niterate = 10)		 	Number of rejection iterations
+	(grow = 1.)		 		Rejection growing radius
+	(scale_conser = yes)		Maintain scale of input image.
+	(obj_only = no)			Normalize only object image?
+
+	(do_rebin = yes)			Rebin data if necessary?
+	(interp_mode = "poly5")		Rebin interpolation method
+	(rb_order = 1)			Order of fitting function
+	(w0 = INDEF)			Starting wavelength
+	(wpc = INDEF)			Wavelength increment
+	(npts = INDEF)			No. of output points
+
+	(ccf_output = "ccfdemo")	Output file/image name for ccf dump
+	(out_type = "image")		Type of output file to create
+	(out_axis = "lag")		X-axis for output
+
+.fi
+.NH 2
+Filter Parameters
+.PP
+The following parameters control filtering of the data while in Fourier
+space.
+.nf
+
+	(filter = yes)			Filter the data before correlation?
+	(filt_type = "ramp")		Filter window type
+	(cuton = 1)				Cuton wavenumber for filter
+	(cutoff = 100)			Cutoff wavenumber for filter
+	(fullon = 10)			Wavenumber at which filter reaches one
+	(fulloff = 200)			Wavenumber at which filter reaches zero
+.fi
+.NH 2
+Fourier Plotting Parameters
+.PP
+The following parameters control filtering of the data while in Fourier
+space.
+.nf
+	(plot = "amplitude")		What form of FFT plot?
+	(overlay = yes)			Overlay the filter function on the plot?
+	(split_plot = yes)		Produce a split plot on the screen?
+	(one_image = "object")		What image is plotted if one screen
+	(when = "before")		Plot FFT before or after filtering
+	(log_scale = yes)		Plot on a log scale?
+	(x_axis = "frequency")		What is the x-axis scaling?
+	(fft_zoom = 4.)			Zoom factor if not displaying whole FFT
+.fi
+
+.NH
+Cross Correlation and Fourier Techniques Used
+.PP
+The requirements and specifications of the correlation and Fourier techniques
+to be used are described below along with the gory detail of the algorithms
+themselves.
+.NH 2
+Requirements and Specifications
+.LP
+The cross correlation techniques used must provide the following operations:
+.IP \(bu
+Each one dimensional correlation must produce a value of the relative shift
+between the object and template spectrum.
+.IP \(bu
+Each value of the shift derived from the correlation function shall have an 
+error estimate attatched to it.
+.IP \(bu
+Each correlation method must be independant of the data format (i.e. longslit
+data which have been averaged into rows, echelle orders, or aperture numbers).
+.IP \(bu
+There shall be no restriction on the length of the data to be operated upon.
+.IP \(bu
+The user shall be able to control the range over which the resulting 
+correlation function is useful.  For example,  the user may filter out 
+wavenumbers that are not to be used in the correlation, adjust the range 
+over which a shift will be searched, or control the number of points in the
+correlation function to be fit.
+.LP
+The following correlation methods will be made available by the package:
+.IP \(bu
+A squared difference method in which an unnormalized correlation function is
+produced by summing the squared difference between the object and template
+spectra at a given trial shift.
+.IP \(bu
+A standard Fourier correlation method in which the data are transformed and
+one multiplied by the conjugate of the other and the resultant inverse 
+transformed to produce a normalized correlation function.
+.IP \(bu
+A Fourier quotient method in which a galaxy and stellar spectrum are transformed
+and their ratio fit to a broadening function, the parameters of which will
+describe the relative line strength, velocity dispersion and redshift of 
+the galaxy spectrum.
+.IP \(bu
+A Fourier difference method in which a galaxy and stellar spectrum 
+are transformed and their difference fit to a broadening function, the 
+parameters of which will describe the relative line strength, velocity 
+dispersion and redshift of the galaxy spectrum.
+.NH 2
+Algorithms
+.PP
+The basic specific algorithms to be employed are briefly described below.
+.NH 3
+Fourier Cross Correlation
+.PP
+The Fourier cross correlation is to be done in the standard way:  The object 
+and template spectrum are transformed into Fourier space and once there the
+object transform is multiplied by the complex conjugate of the template
+transform.  The resultant is then inverse transformed back to real space 
+producing a normalized cross correlation function, the peak of which is
+at a lag corresponding to the pixel shift between the two spectra.  
+The error computation
+and the algorithm in general will follow the work of Tonry & Davis (1979,
+Ast. J, \fI84\fR, 1511).
+.NH 3 
+Squared Difference Correlation
+.PP
+This method is most commonly known at NOAO as "Daryl's program" but actually
+was described by Weiss et al (1978, Astron. Astrophys., \fI63\fR, 247).  The 
+method works as follows:
+.EQ
+	d sub j ~=~ sum from i=n1 to n2 (x sub i ~-~ y sub i+j ) sup 2
+.EN
+where $x sub i$ denotes the intensity of the reference spectrum and $y sub i+j$
+denotes the intensity of the object spectrum at a trial shift $j$.  
+The resulting $d sub j$ array produces a curve whose minimum is at the pixel 
+shift between the two spectra. Unfortunately, this method produces an
+unnormalized correlation function, thus making an estimate of the quality
+of the correlation impossible.
+.NH 3 
+Fourier Quotient Method
+.PP
+This method was first described by Sargent et al (1977, Astrophys. J, \fI212\fR,
+326) and is still a useful method for obtaining velocity dispersions in
+galaxies.  It is assumed that the galaxy spectrum is a convolution of an 
+appropriate mean stellar spectrum with a Doppler broadening function.
+From the convolution theorem then, the
+Fourier transform of the galaxy spectrum would be the product of the transform
+of the stellar spectrum with the transform of the broadening function.  The
+broadening function is usually assumed to be a Gaussian characterized by a
+dispersion $sigma$ and a redshift $z$.
+By computing the transforms of the galaxy and template (stellar) spectra, it is 
+possible to fit the ratio of the galaxy transform to the stellar transform,
+adopting the values of $sigma$ and $z$ which yield the best fit.
+.PP
+Therefore, from the definition of the discrete Fourier transform 
+F(k) of a function F(j), we find that the broadening function is described
+in terms of the transforms of the galaxy spectrum G(j) and the 
+star spectrum S(j) as
+.EQ
+	{ G tilde (k) } over { S tilde (k) } ~~=~~ gamma~ exp left [ - 1 over 2 
+left ( {2 pi ks} over n right ) sup 2 ~+~ { { 2 pi k zeta} over n } right ]~~ ;
+.EN 
+.EQ
+	s ~==~ sigma over { c~ DELTA~ ln lambda} ,~~~~~~~   
+	zeta ~==~ { ln (1 + z) } over { DELTA~ ln lambda }
+.EN
+The parameters \fIs\fR and $zeta$
+are the velocity dispersion and logarithmic redshift measured in pixels 
+respectively.  The parameter $gamma$
+is a normalization factor which measures the strength of the galaxy lines 
+with respect to the stellar lines.
+.NH 3 
+Fourier Difference Method
+.PP
+The Fourier difference method is similar to the quotient method in the
+assumption that a galaxy spectrum can be treated as a mean stellar spectrum
+convolved with a broadening function.  It does, however, try to remedy
+the inherent deficiency of weighting certain points too heavily that
+appears in the Fourier Quotient method. The Fourier difference method is
+best described by noting that the galaxy and stellar spectra are fit to
+each other rather than to the broadening function, thus making the error
+analysis more straightforward.  If the noise in the stellar spectrum
+is negligable, however, then the two methods are comparable.
+.PP
+For a given galaxy spectrum \fIG\fR, a stellar spectrum \fIS\fR, and a 
+broadening function \fIB\fR, we wish to minimize the residual in the Fourier 
+domain denoted
+by
+.EQ
+	chi tilde sup 2 ~=~ sum from j=0 to N-1 ~( G tilde "" sub j sup * ~-~ 
+B tilde "" sub j sup * G tilde "" sub j sup * )~( G tilde "" sub j ~-~ 
+B tilde "" sub j G tilde "" sub j ) 
+.EN
+Where $G tilde$, $S tilde$, and $B tilde$ are the Fourier transforms of
+the galaxy, star, and broadening function respectively.
+This should simplify the numerical fitting because the convolution is now
+a simple multiplication in Fourier space.
+
+.NH
+Remaining Task Algorithms
+.PP
+\fBNOTE:\fI  At this writing, the details of these algorithms are not 
+yet defined.\fR
+.NH 2
+Telluric Line Removal
+.PP
+A task shall be written to automatically remove telluric or other artificial
+features.  The cross correlation techniques will be employed to compute the
+relative shift between the object and template spectra.  The relative line
+depths will also be computed and the spectra divided to remove the lines
+in the template spectrum from the object spectrum.  
+.NH 2
+Fitting (Emmision) Line Profiles
+.PP
+A task shall be written to do line profile fitting for the purpose of velocity
+analysis.  It will be possible to trace the various profile parameters (center,
+width, etc) and derive velocity information.  This task may also be used to
+do postprocessing of the correlation function.
+
+.NH
+Filtering of the Data in Fourier Space
+.PP
+To remove noise in the data once it has been transformed into the Fourier
+domain, it must be possible to filter out unwanted frequencies from the data.
+Filtering the data in the Fourier domain by attenuating or eliminating 
+certain frequencies has the same effect as smoothing the data in real space.
+Since the data are assumed to be binned linearly in log wavelength, no 
+phase shifts are introduced by the filtering.
+.NH 2
+Requirements and Specifications
+.LP
+The following filtering requirements must be met
+.IP \(bu
+A choice of filtering functions must be made available to the user.
+.IP \(bu
+The user must specify the wavenumbers over which the filter will operate.
+.IP \(bu
+The data must be binned linearly with the logarithm of the wavelength so as
+not to introduce any phase shifts when filtering.
+.IP \(bu 
+Filtering of data must be possible from any of the tasks using Fourier 
+techniques.
+.IP \(bu
+Those wavenumbers outside the specified cuton and cutoff numbers will be set to
+zero, while those inside the range will be attenuated according to the
+filter function chosen.
+.IP \(bu
+The specified range over which the filter extends must be the same for both the
+object and reference spectrum.
+.LP
+The following filtering functions will be made available to the user:
+.IP \(bu
+\fBSquare\fR - A square step function in which the user specifies the
+beginning and ending wavenumbers.
+.IP \(bu
+\fBRamp\fR - A ramp function in which the user must specify the cuton
+wavenumber, the wavenumber at which the filter reaches full value, the
+wavenumber at which the filter begins to decline and the cutoff wavenumber.
+.IP \(bu
+\fBHanning\fR -  The user must specify the cuton and cutoff wavenumbers.
+The data are attentuated according to the function:
+.EQ
+w sub j  ~=~ 1 over 2 left [ 1. ~-~ cos left ( { 2 pi j } over { N-1 } right ) right ]
+.EN
+.nf
+.na
+		where 	j =  (wavenumber - cuton_wavenumer) 
+			  N =  (cutoff - cuton) + 1
+.ad
+.fi
+.IP \(bu
+\fBWelch\fR - The user must specify the cuton and cutoff wavenumbers.
+The data are attentuated according to the function:
+.EQ
+w sub j ~=~ 1 ~-~ left [ { j ~-~ 1 over 2 ( N - 1 ) } over { 1 over 2 ( N + 1 ) } right ] sup 2
+.EN
+.nf
+.na
+		where 	j =  (wavenumber - cuton_wavenumer) 
+			  N =  (cutoff - cuton) + 1
+.ad
+.fi
+
+.NH
+Dispersion Calculations
+.PP
+Often times when computing the velocity dispersion from a correlation function,
+the simplest thing to be done is to convert the full width at half maximum 
+(FWHM) of the fitted peak to a velocity.  However, this is not fully correct
+since the width of the correlation function is "an average of the widths of
+galaxy lines quadratically added to the widths of template lines, and is
+therefore the quadratic sum of two stellar widths and the velocity broadening
+width".  If the function fit to the peak is a polynomial (e.g a parabola),
+what is required is a method in which to convert a simple FWHM pixel width of 
+the ccf to a true dispersion.  
+.PP
+When the correlation peak is fit and a width determined, we must define 
+a relationship between the width $w$ and the width of a Gaussian profile
+(the intrinsic dispersion), $gamma$.  For a given fit to the
+peak, this can be expressed (following Tonry & Davis) as
+.EQ
+gamma ~=~ f(w) ~=~ s sub 1 ~+~ s sub 2 w ~+~ s sub 3 w sup 2 ~+~ s sub 4 w sup 3
+.EN
+.LP
+The coefficients for this function are computed by empirically convolving
+Gaussians of known velocity width with stellar spectra, thus producing
+a plot of dispersion versus width which can be fit to obtain the coefficients
+of the polynomial.
+It must be remembered that the coefficients $s sub i$ must be recalculated
+at each new instrumental setup since the function $f(w)$ is used to also
+remove the instrumental distortions that can be caused by varying slit widths.
+.PP
+The \fIrvdisp\fR task may be used to compute the polynomial coefficients
+and produce a database record of the input parameters and coefficients
+that will be used bythe correlation tasks.  Multiple records per file
+are permitted, allowing for varying instrumental setups and parameters since
+the correlation tasks will search for a match of parameters.
+.NH 2
+Requirements and Specifications
+.PP
+To meet the needs of the astronomer in calculating dispersions, a task will
+be written that meets the following specifications:
+.IP \(bu
+The user must specify the number of points to be computed, the velocity
+increment,  and the starting dispersion velocity,
+thus producing a lookup table at a specified resolution.
+.IP \(bu
+The user will specify the name of a database file which will contain the
+$s sub i$ coefficients as well as the points used in the fit and parameters
+of the task.
+.IP \(bu
+Each of the tasks that can compute a dispersion can be furnished the
+name of this database file and use the information contained to compute
+a dispersion value from the width of the correlation function.
+.IP \(bu
+The task will be able to run in interactive or batch mode.  In batch mode the
+task will compute the dispersions and output to the database automatically.
+In interactive mode the user may adjust parameters as in other tasks in this
+package, allowing him to produce database files for various instrumental
+setups at one time.
+.IP \(bu
+The task must be able to call one of the other one dimensional correlation
+routines to compute the correlation functions.
+.IP \(bu
+The task must be able to call one of the other available fitting functions.
+.IP \(bu
+The task must be able to filter the data if a Fourier method is chosen.
+
+.NH
+Fitting Functions
+.PP
+A set of non-linear least squares routines is needed to fit the computed
+correlation function to obtain a shift, or to fit the entire spectum to 
+flatten it.  Polynomial fitting routines are well known and easy enough to
+implement, but we also require more complex functions.  Not only is it 
+desireable to fit a parabola (second order polynomial) to the peak of the
+correlation function (which is a real function), but 
+a Gaussian is sometimes desired.  Also, when
+fitting the ratio or difference between the transforms of the galaxy and
+stellar spectra, a gaussian is needed to fit the complex transform of the
+broadening function.
+.PP
+Since a variety of fitting functions are needed and to ease in the 
+incorporation of other fitting functions in the future, the non-linear
+least squares package \fInlfit\fR written by Lindsay Davis for the \fIAPPHOT\fR
+package will be used.  This has the distinct advatange that all that is
+required to add a new function is to write routines to evaluate the
+function and it's derivatives, simplifying things greatly.
+.NH 2
+Requirements and Specifications
+.PP
+The following fitting functions will be provided and are chosen through
+the tasks parameters or commands:
+.KS
+.IP \(bu
+Parabola.
+.IP \(bu
+One dimensional real Gaussian.
+.IP \(bu
+One dimensional complex Gaussian.
+.IP \(bu 
+$N sup th$-order polynomial.
+.KE
+
+.EQ
+delim off
+.EN
+.NH
+Tasks
+.PP
+The required tasks for this package are the following:
+.nf
+
+.na
+    mkbins		- Create bins of approximately equal flux intensity
+    observatory	- Observatory location database
+    processpars	- Batch processing parameters for RV package
+    filterpars		- Edit the filter function parameters 
+    rvcorrect		- Compute radial velocity corrections
+    rvdisp		- Produce velocity dispersions from CCF widths
+    rvemfit		- Fit emmission features in spectra
+    rvfdiff		- Redshifts and dispersions via Fourier Difference techniques
+    rvfquot		- Redshifts and dispersions via Fourier Quotient techniques
+    rvkeywords	- Keyword translation table for RV image headers
+    rvselect		- Select output fields from an RV record 
+    rvskyline		- Telluric line removal/fitting task
+    rvstats		- Print information to aide in RV parameter selection
+    rvsummary	- Print a summary table of output from RV tasks
+    rvsqdiff		- Radial velocities via a squared difference correlation
+    rvxcor 		- Radial velocities via Fourier cross correlation
+    xcor2d		- Cross correlation of two dimensional data
+.ad
+.fi
+
+.NH 2
+Usage
+.LP
+Some examples of typical usage are listed below.
+.IP \(bu
+A user has a series of Longslit spectra of galaxies at differing position
+angles and wishes to correlate them with a template spectrum to 
+obtain redshift and dispersion information.  
+The user then uses the \fIrvfdiff\fR
+or \fIrvfquot\fR tasks to correlate the spectra and compute the dispersions.
+.IP \(bu
+A user is interested in obtaining radial velocities of a series of spectra
+obtained over several nights with different instrumental setups.  
+The \fIrvdisp\fR task is used to create dispersion tables for each instrumental
+setup.  One of the correlation tasks is then used to correlate each set 
+of spectra.
+.IP \(bu
+A user has a small series of unusual spectra of different spectral types 
+and wishes to obtain radial velocities.
+The \fIrvdisp\fR task is used to create dispersion tables for each instrumental
+setup.  The user then chooses the correlation method he wishes to use and 
+interactively adjusts parameters for each object spectrum, writing the results 
+to the logfile when satisfied.
+.IP \(bu
+A user has a large number of low signal-to-noise spectra to be correlated 
+to obtain a list of radial velocities.
+The \fIrvdisp\fR task is used to create dispersion tables for each new 
+instrumental setup (if any).  The user then chooses the correlation method 
+he wishes to use and after setting up the parameters, processes the list
+as a background job.  After returning from coffee, he examines the
+output list and graphics spool file for bad fits which can be done by hand
+later.
+.IP \(bu
+A user has an old set of spectra for which he was only able to obtain an
+observed radial velocity and wishes to do the heliocentric velocity corrections.
+The user may then use the use the \fIimages.hedit\fR tasks to insert the 
+observed velocity into the image header.  The \fIrvcorrect\fR task is then
+called to correct each image with respect to the sun (or even the Local 
+Standard of Rest).
+
+.NH 1
+Bibliography
+.PP
+.XP
+Press, W.H. et al 1986, \fINumerical Recipes\fR, Cambridge Univ. Press, 
+	Cambridge, Ch 12.
+.XP
+Rabiner, L.R. and Gold, B. 1975 \fITheory and  Application  of Digital
+	Signal Processing\fR, Prentice Hall,  Englewood  Cliffs, Ch 3.
+.XP
+Sargent, Schechter, Boksenberg and Shortridge, 1977, "Velocity Dispersions
+	for 13 Galaxies", \fIAstrop. J.\fR \fB212\fR p326.
+.XP
+Tonry, J. and Davis,  M.  1979,  "A  Survey  of Galaxy Redshift. I. Data
+	Reduction  Techniques",  \fIAstron.  J.\fR  \fB84,\fR  p 1511
+.XP
+Weiss, W.W. et al 1978, "A  Statistical  Approach  for  the  Determination
+	of Relative Zeeman and Doppler Shifts in Spectrograms", \fIAstron. 
+	Astrophys.\fR \fB63\fR, p 247. 
+.XP
+Willmarth, D.W and Abt, H.A., 1985, "Radial Velocities From CCD Detectors" 
+	in \fIIAU Coll. No.  88,  Stellar  Radial  Velocities\fR,  p 99
+.XP
+Wyatt, W.F., 1985, "The  CfA  System  for  Digital  Correlations"   in 
+	\fIIAU Coll. No 88,  Stellar  Radial Velocities\fR, p 123
+.PP
+
+.NH
+Detailed Manual Pages
+.PP
+	The individual manual pages for these tasks follow this document.
diff --git a/noao/rv/doc/rvplan.ms b/noao/rv/doc/rvplan.ms
new file mode 100644
index 00000000..7b81ee1a
--- /dev/null
+++ b/noao/rv/doc/rvplan.ms
@@ -0,0 +1,91 @@
+.OM
+.TO
+RV folks
+.FR
+Doug Tody
+.SU
+RV development plans
+.PP
+The purpose of this memo is to introduce the RV "level zero specifications"
+document enclosed, to explain what that means and what our plans for future
+RV package development are, and how the new programming team approach being
+used for RV and other projects works.
+.SH
+Programming Teams
+.PP
+As was mentioned in our RV meeting a while back, we are experimenting
+with the use of small programmer teams for major projects such as RV.
+In the case of RV, the programming team is Mike and Frank, with Mike being
+the programmer in charge of the project, and Frank the reviewer and critic.
+Frank and Mike work together on a daily basis and every few weeks the three
+of us have a team meeting to review progress.  Similar teams are being set
+up for other projects, e.g., Mike (reviewer-critic) and Lindsey (programmer)
+are the team for the new PHOTCAL package.
+.PP
+For each project we maintain a project directory where all design
+specifications, email, etc. for the project are kept.  You are welcome
+to browse this if you wish to know more about the details of the project.
+In the case of RV, the project directory is /u2/fitz/iraf/rvproject on
+tucana.  All of the email exchanged by the team members during the package
+design, or mail exchanged with scientists or other users, is saved in the
+rvmail file in this directory.  If you have detailed comments on any feature
+of a package like RV, it is best to send them to one of the team members via
+email so that they get logged for the rest of us to read.
+.SH
+RV Development Plans
+.PP
+Based upon your input in the RV review meeting a while back, we have come
+up with the following plan for the next phase in the development of the
+RV package.  This plan is intended to serve our immediate needs for radial
+velocity analysis as quickly as possible, while providing a fully featured
+package in the longer term.
+.RS
+.IP \(bu
+\fBLevel Zero Task\fR.  This is intended to provide a basic radial
+velocity capability, providing the most needed functions but avoiding
+the more ambitious features planned for the eventual full IRAF
+package.  It is the specifications for the level zero task which are
+enclosed for you to review and comment on.  Once completed, the level
+zero task will be frozen and will continue to be available
+indefinitely, without change, providing a stable tool for basic radial
+velocity analysis while development and testing of the full package
+goes forward.  Although the level zero task will provide limited
+functionality, those algorithms and features provided are intended to
+be about as good as can be done (please let us know if you think
+otherwise!) and will have undergone lots of testing with real and
+artificial data by the time the software is released.
+.IP \(bu
+\fBBaseline Package\fR.  This will be more or less what Mike has in the
+current prototype version of RV, most likely with many changes reflecting
+what we learn from the level zero task.
+.IP \(bu
+\fBFull Package\fR.  This will be a second version of the baseline release
+adding all the desirable but lower priority functions.  Many changes to the
+baseline package are sure to be needed once user testing begins, and these
+will be incorporated into the full package along with the remaining tasks
+not planned for the baseline package.
+.RE
+.PP
+In addition to the above, the current prototype RV package will continue
+to be available for use while the new software is under development.
+.PP
+As you will see from the draft specifications prepared by Mike and
+Frank, the level zero task provides fourier cross correlation for both
+raw pixel arrays and wavelength calibrated data, including those
+features we thought were necessary for even the level zero task for it
+to be useful.  These include automatic log-lambda mapping of the input
+data, continuum fitting and subtraction, fourier filtering, weighting
+of the correlation peak fit to minimize sampling errors, and optional
+correction to heliocentric velocities.  Important changes to the user
+interface have also taken place.  The database capabilities (RVSELECT)
+have been left out, but will be provided in the baseline version of the
+package (the lists.fields task can be used to make lists of selected
+quantities from the output of the level zero task).  Other important
+but less essential functions such as the fourier quotient algorithm,
+redshift and deredshift functions, etc., will also be deferred to the
+baseline package.
+.PP
+Comments on our plans for further development of the package, or the
+draft specifications for level zero, are most welcome.  If you need
+some feature in level zero which doesn't appear to be there, try to let
+us know as soon as possible.
diff --git a/noao/rv/doc/rvreidlines.hlp b/noao/rv/doc/rvreidlines.hlp
new file mode 100644
index 00000000..763e813a
--- /dev/null
+++ b/noao/rv/doc/rvreidlines.hlp
@@ -0,0 +1,405 @@
+.help rvreidlines Aug93 noao.rv
+.ih
+NAME
+rvreidlines -- Reidentify spectral lines and measure velocities
+.ih
+USAGE
+rvreidlines reference images
+.ih
+PARAMETERS
+.ls reference
+Spectrum with previously identified features to be used as reference for
+other spectra.  If there are multiple apertures, lines, or columns in the
+image a master reference is defined by the \fIsection\fR parameter.
+The other apertures, lines, or columns selected by \fIstep\fR are
+reidentified if needed.
+.le
+.ls images
+List of dispersion corrected spectral images in which the features in the
+reference image are to be reidentified.  In two and three dimensional
+images the reidentifications are done by matching apertures, lines,
+columns, or bands with those in the reference image.
+.le
+.ls interactive = no
+Examine and fit features and velocities interactively?  If the task is run
+interactively a query (which may be turned off during execution) will be
+given for each vector reidentified after printing the results of the
+automatic determination and the user may chose to enter the interactive
+\fBrvidlines\fR task.
+.le
+.ls section = "middle line"
+If the reference image is not one dimensional or given as a one dimensional
+image section then this parameter selects the master reference image
+vector.  The master reference is used when reidentifying other vectors in
+the reference image or when other images contain apertures not present in
+the reference image.  This parameter also defines the direction
+(columns, lines, or z) of the image vectors to be reidentified.
+
+The section parameter may be specified directly as an image section or
+in one of the following forms
+
+.nf
+line|column|x|y|z first|middle|last|# [first|middle|last|#]]
+first|middle|last|# [first|middle|last|#] line|column|x|y|z
+.fi
+
+where each field can be one of the strings separated by | except for #
+which is an integer number.  The field in [] is a second designator which
+is used with 3D data.  See the example section for \fBrvidlines\fR for
+examples of this syntax.  Abbreviations are allowed though beware that 'l'
+is not a sufficient abbreviation.
+.le
+.ls newaps = yes
+Reidentify new apertures in the images which are not in the reference
+image?  If no, only apertures found in the reference image will be
+reidentified in the other images.  If yes, the master reference spectrum
+is used to reidentify features in the new aperture and then the
+new aperture features will be added to the reference apertures.  All
+further identifications of the new aperture will then use this result.
+.le
+.ls override = no
+Override previous solutions?  If there are previous measurements for a
+particular image vector being identified, because of a previous
+\fBrvidlines\fR or \fBrvreidlines\fR, this parameter selects whether
+to simply skip the reidentification or do a reidentification and
+velocity measurement and overwrite the results in the logfile and database.
+.le
+
+The following parameters are used for selecting and reidentifying additional
+lines, columns, or apertures in two dimensional formats.
+.ls trace = no
+There are two methods for defining additional reference lines, columns, or
+bands in two and three dimensional format images as selected by the
+\fIstep\fR parameter.  When \fItrace\fR is no the master reference line or
+column is used for each new reference vector.  When this parameter is yes
+then as the reidentifications step across the image the last reidentified
+features are used as the reference.  This "tracing" is useful if there is a
+coherent shift in the features such as with long slit spectra.  However,
+any features lost during the tracing will be lost for all subsequent lines
+or columns while not using tracing always starts with the initial set of
+reference features.
+.le
+.ls step = "10"
+The step from the reference aperture, line, column, or band used for
+selecting and/or reidentifying additional lines, columns, or bands in a two
+or three dimensional reference image.  For three dimensional images there
+may be two numbers to allow independent steps along different axes.  For
+multiaperture images the step is typically 1 while for long slit or
+Fabry-Perot images the step is large enough to map any significant changes
+in the feature positions.  If the step is zero then only the reference
+line, column, or band is used.
+.le
+.ls nsum = "10"
+Number of lines, columns, or bands across the designated vector axis to be
+summed when the image is a two or three dimensional spatial spectrum.
+It does not apply to multispec format spectra.  If the image is three
+dimensional an optional second number can be specified for the higher
+dimensional axis  (the first number applies to the lower axis number and
+the second to the higher axis number).  If a second number is not specified
+the first number is used for both axes.
+.le
+.ls shift = "0"
+Shift in user coordinates to be added to the reference features before
+centering when stepping to other lines, columns, or bands in the reference
+image.  Generally no shift is used by setting the value to zero.
+The shift is used as a slope with positive values increasing towards
+larger line or column numbers.  This parameter is not used for
+reidentifications from the reference image to other images.
+If the image is three dimensional then two numbers may be specified
+for the two axes.
+.le
+.ls nlost = 0
+When reidentifying features by tracing, if the number of features not found
+in the new image vector exceeds this number then the reidentification
+record is not written to the logfile and database and the trace is terminated.  A warning is printed in the log and in the verbose output.
+.le
+
+The following parameters define the finding and recentering of features.
+See also \fBcenter1d\fR and \fBrvidlines\fR.
+.ls cradius = 5.
+Centering radius in pixels.  If a reidentified feature falls further
+than this distance from the previous line or column when tracing or
+from the reference feature position when reidentifying a new image
+then the feature is not reidentified.
+.le
+.ls threshold = 10.
+In order for a feature center to be determined, the range of pixel
+intensities around the feature must exceed this threshold.  This parameter
+is used to exclude noise peaks and terminate tracing when the signal
+disappears.  However, failure to properly set this parameter, particularly
+when the data values are very small due to normalization or flux
+calibration, is a common error leading to failure of the task.
+.le
+
+The following parameters select and control the automatic addition of
+new features during reidentification.
+.ls addfeatures = no
+Add new features from a line list during each reidentification?  If
+yes then the following parameters are used.  This function can be used
+to compensate for lost features from the reference solution, particularly
+when tracing.  Care should be exercised that misidentified features
+are not introduced.
+.le
+.ls coordlist = ""
+User coordinate list consisting of an ordered list of rest spectral line
+coordinates.
+.le
+.ls match = 10.
+The maximum difference for a match between the feature coordinate function
+value and a coordinate in the coordinate list (after correction by the
+velocity).
+.le
+.ls maxfeatures = 50
+Maximum number of the strongest features to be selected automatically from
+the coordinate list.
+.le
+.ls minsep = 2.
+The minimum separation, in pixels, allowed between feature positions
+when defining a new feature.
+.le
+
+The following parameters determine the input and output of the task.
+.ls database = "database"
+Database containing the feature data for the reference image and in which
+the features for the reidentified images are recorded.
+.le
+.ls logfiles = "logfile"
+List of file in which to record the velocity results and to keep a
+processing log.  If a null file, "", is given then no log is kept.
+.le
+.ls verbose = no
+Print reidentification and velocity information on the standard output?
+.le
+.ls keywpars = ""
+The image header keyword translation table as described in 
+the \fIkeywpars\fR named pset.  This defines the header keywords used
+to obtain the observation information needed for computing the
+heliocentric velocity.
+.le
+.ls graphics = "stdgraph"
+Graphics device.  The default is the standard graphics device which is
+generally a graphics terminal.
+.le
+.ls cursor = ""
+Cursor input file.  If a cursor file is not given then the standard graphics
+cursor is read.
+.le
+ADDTIONAL PARAMETERS
+The measured velocities are corrected to a heliocentric frame of reference
+if possible.  This requires determining various parameters about the
+observation.  The latitude, longitude, and altitude of the observation
+are determined from the observatory database.  The observatory is
+defined by either the OBSERVAT image header keyword or the "observatory"
+package parameter in that order.  See the help for \fBobservatory\fR
+for additional information.
+
+The date, universal time, right ascension, declination, and coordinate epoch
+for the observation are obtained from the image header.  The keywords
+for these parameters are defined in the \fBkeywpars\fR parameter set.
+.ih
+DESCRIPTION
+\fBRvreidlines\fR takes spectral lines previously identified in a reference
+image and recorded in a database and identifies them in other spectra and
+determines a radial velocity.  If the images are
+two or three dimensional or multiaperture format and a \fIstep\fR greater
+than zero is specified then additional vectors
+(lines/columns/bands/apertures) in the reference image will be reidentified
+from the initial master reference vector (as defined by an image section or
+\fIsection\fR parameter) provided they have not been reidentified
+previously or the \fIoverride\fR flag is set.  For multiple aperture
+spectra images, called multiaperture, the step size is typically 1; i.e.
+reidentify features in all spectra.  For two and three dimensional images,
+such as long slit and Fabry-Perot spectra, the step(s) should be large enough
+to minimize execution time and storage requirements but small enough to
+follow shifts in the features (see the discussion below on tracing).  The
+set of reference identifications is applied to other images in the same
+lines, columns, bands, or apertures.  In multiaperture images the same
+apertures are matched in the reference image regardless of actual line
+order; i.e.  the apertures need not be in the same order or even have all
+apertures present.
+
+The reidentification of other features in other reference image vectors
+may be done in two ways selected by the parameter \fItrace\fR.  If not
+tracing, the initial reference vector is applied to the other selected
+vectors.  If tracing, the reidentifications are made with respect to the
+last set of identifications as successive steps away from the reference
+vector are made.  The tracing method is appropriate for two and three
+dimensional spatial images, such as long slit and Fabry-Perot spectra, in
+which the positions of features traced vary smoothly.  This allows
+following large displacements from the initial reference by using suitably
+small steps.  It has the disadvantage that features lost during the
+reidentifications will not propagate (unless the \fIaddfeatures\fR option
+is used).  By not tracing, the original set of features is used for every
+other vector in the reference image.
+
+When reidentifying other vectors in the reference image the parameter
+\fBshift\fR may be used to add a shift(s) to the features positions
+before recentering.  The shift is added to lines, columns, or bands, greater
+than the current line, column, or band and subtracted if less.  If tracing
+the shifts are the same from step to step while if not tracing the
+shifts are added to the shifts from the previous step.  Thus, in both
+cases an approximation of a slope is used.  This allows large
+slopes in the features to be followed even when not tracing but the 
+shift value must be predetermined.
+
+When tracing, the parameter \fInlost\fR is used to terminate the
+tracing whenever this number of features has been lost.  This parameter,
+in conjunction with the other centering parameters which define
+when a feature is not found, may be useful for tracing features
+which disappear before reaching the limits of the image.
+
+When reidentifying features in other images, the reference
+features are those from the same aperture, line, column, or band of the
+reference image.  However, if the \fInewaps\fR parameter is set
+apertures in multiaperture spectra which are not in the reference
+image may be reidentified against the master reference aperture and
+added to the list of aperture to be reidentified in other images.
+This is useful when specta with different aperture numbers are
+stored as one dimensional images.
+
+There are two centering algorithms; a flux bisecting algorithm called
+\fBcenter1d\fR and a gaussian fitting algorithm.  These algorithms
+are described in the help for \fBrvidlines\fR.  The algorithm used
+and whether the feature is emission or absorption is the same one used
+in the reference image.  The only caveat is that multiple gaussian
+fitting provided by the interactive 'b' key in \fBrvidlines\fR is
+not done by this task and those lines will be fit by gaussians
+independently.
+
+When recentering, if a feature position shifts by more than the
+amount set by the parameter \fIcradius\fR from the starting position
+(possibly after adding a shift) or the feature strength (peak to valley) is
+less than the detection \fIthreshold\fR then the new feature is discarded.
+The \fIcradius\fR parameter should be set large enough to find the correct
+peak in the presence of any shifts but small enough to minimize incorrect
+identifications.  The \fIthreshold\fR parameter is used to eliminate
+identifications with noise.  Failure to set this parameter properly for the
+data (say if data values are very small due to a calibration or
+normalization operation) is the most common source of problems in using
+this task.
+
+In two and three dimensional images, though not multiaperture images, the
+number of lines, columns, or bands given by the parameter \fInsum\fR are summed
+to form the one dimensional image vector in which the features are
+identified.  This increases the accuracy for reidentifying weak
+features.
+
+If the parameter \fIaddfeatures\fR is set additional features may be added
+after the initial reidentification and velocity determination using a line
+list of rest wavelengths.  A maximum number of added features, a matching
+distance in user coordinates, and a minimum separation from other features
+are additional parameters.  This option is similar to that available in
+\fBrvidlines\fR and is described more fully in the help for that task.
+
+A statistics line is generated for each reidentified vector.  The line
+contains the name of the image being reidentified (which for two
+dimensional images includes the image section and for multiaperture
+spectra includes the aperture number), the number of features found
+relative to the number of features in the reference, the number of
+features used in the velocity determination (currently there is
+no rejection of lines) relative to the number found,  the
+mean pixel and user coordinate shfits relative to the reference
+coordinates, and the measured velocity and RMS in the velocity.
+The velocity is the heliocentric velocity if the necessary observation
+information in the image and observatory database are found.
+
+If the task is run with the \fIinteractive\fR flag the statistics line
+is printed to the standard output (the terminal) and a query is
+made whether to fit the lines and measure the velocity interactively.
+A response
+of yes or YES will put the user in the interactive graphical mode
+of \fBrvidlines\fR.  See the description of this task for more
+information.  The idea is that one can monitor the statistics information,
+particularly the velocity RMS, and select only those which may be
+questionable to examine interactively.  A response of no or NO will
+continue on to the next spectrum.  The capitalized responses
+turn off the query and act as permanent response for all other
+reidentifications.
+
+This statistics line, including headers, is written to any specified
+log files.  The log information includes the image being
+reidentified and the reference image.
+In addition the set of lines, the observatory information used,
+and the computed observed and heliocentric velocities and redshifts
+are recorded.  This is the same information as is produced
+by \fBrvidlines\fR.
+.ih
+DATABASE RECORDS
+The database specified by the parameter \fIdatabase\fR is a directory of
+simple text files.  The text files have names beginning with 'id' followed
+by the entry name, usually the name of the image.  The database text files
+consist of a number of records.  A record begins with a line starting with the
+keyword "begin".  The rest of the line is the record identifier.  Records
+read and written by \fBrvreidlines\fR have "identify" as the first word of the
+identifier.  Following this is a name which may be specified following the
+":read" or ":write" commands.  If no name is specified then the image name
+is used.  For 1D spectra the database entry includes the aperture number
+and so to read a solution from a aperture different than the current image
+and aperture number must be specified.  For 2D/3D images the entry name
+has the 1D image section which is what is specified to read the entry.
+The lines following the record identifier contain
+the feature information and redshift (without heliocentric correction).
+
+The database files have the name "identify" and the prefix "id" because
+these files may also be read by the \fBidentify\fR task for changing
+the dispersion function based on the rest wavelengths.
+.ih
+EXAMPLES
+1.  To generate a rotation curve for a long slit spectrum of a
+galaxy first use \fBrvidlines\fR to mark some lines at the center of the
+galaxy.  If the velocities are to be absolute then you give the rest
+wavelengths and do a fit.  However to get velocities relative to the center
+use the measured wavelengths by simply accepting the prompted measured
+wavelengths.  Then run \fBrvreidlines\fR.  The \fInsum\fR and \fIstep\fR
+parameters allow controlling the summing size and spacing.
+
+.nf
+    rv> rvid lsgal sec="mid col" nsum=5
+	    Mark lines and then quit.
+    Write velocity data to the logfile (yes)?
+    Write feature data to the database (yes)?
+    rv> rvreid lsgal "" sec="mid col" nsum=5 step=5 trace+ v+
+
+    RVREIDLINES: NOAO/IRAF V2.10.3 valdes Sat 14:47:55 21-Aug-93
+      Reference image = lsgal, New image = lsgal
+     Image Data  Found    Fit  Pix Shift  User Shift Velocity    RMS
+    lsgal[45,*]    7/7    7/7    -0.0181     -0.0212    -1.37   11.3
+    lsgal[40,*]    7/7    7/7     0.0147      0.0193     1.34   8.73
+    lsgal[35,*]    7/7    7/7     0.0931       0.116     8.01   9.16
+    lsgal[30,*]    7/7    7/7    -0.0224     -0.0265    -1.78   27.6
+    lsgal[25,*]    7/7    7/7     0.0558        0.07     4.83   33.7
+    lsgal[20,*]    7/7    7/7    -0.0317     -0.0379    -3.08   33.6
+    lsgal[15,*]    5/7    5/5      0.015      0.0201    0.799   43.7
+    lsgal[10,*]    7/7    7/7      0.395       0.489     33.7   54.9
+    lsgal[5,*]     4/7    4/4      -1.22       -1.51    -106.   84.3
+    lsgal[55,*]    7/7    7/7      0.014      0.0184     1.41   10.5
+    lsgal[60,*]    7/7    7/7    -0.0897      -0.109    -7.59   7.21
+    lsgal[65,*]    7/7    7/7    -0.0109     -0.0122   -0.957   10.9
+    lsgal[70,*]    7/7    7/7     -0.074     -0.0902    -6.55   14.6
+    lsgal[75,*]    7/7    7/7   -0.00203    -0.00136    0.227   54.3
+    lsgal[80,*]    6/7    6/6       0.08      0.0997     6.66   96.7
+    lsgal[85,*]    6/7    6/6      0.289       0.357     27.2   104.
+    lsgal[90,*]    6/7    6/6      0.459       0.568     40.5   33.2
+    lsgal[95,*]    6/7    6/6      0.926        1.14     78.5   65.5
+    lsgal[100,*    5/7    5/5      0.696        0.86     59.1   44.2
+    rv> match Vobs logfile | fields "" 2,6,11 | \
+    >>> graph point- mark=vebar szmark=-1
+.fi
+
+The last command extracts the Vobs results from the logfile using
+\fBmatch\fR, the column number, velocity, and mean error are extract
+using \fBfields\fR, and graphs the points with error bars.  One
+drawback to this method is that the nubmer of columns summed is
+constant and so the signal-to-noise decreases with the galaxy light.
+.ih
+REVISIONS
+.ls RVREIDLINES V2.11
+This task will now work in the units of the input spectra.
+.le
+.ls RVREIDLINES V2.10.3
+This task in new in the version.
+.le
+.ih
+SEE ALSO
+center1d, fxcor, keywpars, observatory, rvcorrect, rvidlines
+.endhelp