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+.help daophot Sep87 "Crowded Field Stellar Photometry'
+.sh
+1. Introduction
+
+     The DAOPHOT package will provide a set of routines for performing
+stellar photometry on crowded fields in either interactive or batch mode.
+DAOPHOT works by fitting an empirical point spread function (PSF)
+to each object in the field
+allowing for overlap of closely spaced images. This document presents the
+the requirements and specifications for the package and describes some of
+the algorithms to be used. Most of the algorithms are described in
+the original article by Peter Stetson (1987 P.A.S.P. 99,191).
+
+.sh
+2. Requirements
+.ls 4
+.ls (1)
+The tasks in the DAOPHOT package shall take as input an IRAF imagefile
+containing two-dimensional image data which has been corrected for 
+pixel to pixel gain variations, high frequency variations in the background,
+any nonlinearitys in the data except for those which can be specified as
+a lower and/or upper bound,
+and any other instrumental defects affecting the intensity value of an
+individual pixel. However, it shall be possible to exclude bad pixels,
+rows or columns from analysis by DAOPHOT routines in a very crude manner.
+.le
+.ls (2)
+The tasks in the package which produce tabular output shall use the
+SDAS Tables for their output and those tasks which read output from other
+DAOPHOT tasks will be able to read SDAS Tables. In the future the input/output
+shall make use of the DBIO package.
+.le
+.ls (3)
+The DAOPHOT package shall work in conjunction with the APPHOT package produced
+at NOAO. DAOPHOT will not have any provision to do aperture photometry of its
+own. The output format from DAOPHOT tasks will be consistent with APPHOT.
+.le
+.ls (4)
+Given as input a reduced two-dimensional image which has been processed by the
+APPHOT package, the DAOPHOT package shall be able to perform the following
+functions:
+.ls 4
+.ls o
+Interactively define a PSF for the data frame. The PSF will be defined 
+empirically from one or more stars in the field. The task to determine the
+PSF shall be interactive and the user shall be able to use a
+graphics terminal and/or an image display device to select the stars which
+will make up the PSF. The user will be able to evaluate the PSF through 
+different means including contour plots, 3-d mesh plots, and displaying the
+PSF on an image display device.
+The user shall be able to "mask" out parts of the PSF which may be contaminated 
+by nearby stars, bad pixels etc. Only the non-masked portions of the PSF will
+be used in the fitting routines.
+.le
+.ls o
+Fit the PSF simultaneously to groups of stars in the image frame whose 
+images overlap to some degree. The parameters in the fit shall include the
+the object brightness, X and Y position of the star and potentially the sky
+background. The sky shall be able to be specified as either a flat uniform
+background or a simple tilted planar sky. The photometry routines shall
+produce realistic errors in the photometry assuming that realistic numbers
+for the characteristics of the data are input.
+.le
+.ls o
+Subtract the fitted stars from the data frame to produce a subtracted 
+image for further analysis.
+.le
+.ls o
+Add artificial stars to the data frame in order to check accuracy and
+completeness in the photometry. The user shall have control over the
+number of stars added, the brightness range, the area of the image to contain
+the added stars and the noise characteristics of the added stars.
+.le
+.le
+.ls (5)
+The DAOPHOT package shall include tasks to inspect and edit the results from the
+photometry routines. These shall include tasks such as interactively
+rejecting particular stars from the results, 
+producing plots of errors versus brightness, errors versus position etc. 
+.le
+.ls (6)
+The DAOPHOT package shall provide utility packages to handle the output
+data from the fitting routines. These shall include such tasks as 
+aperture growth curves, photometric calibrations, color-magnitude and
+color-color diagrams.
+.le
+.ls (7) 
+The DAOPHOT routines shall optionally keep a history file to keep 
+track of the processing done on the images. This will include the values of
+various parameters used in the various tasks of the DAOPHOT package.
+.le
+.ls (8) 
+The tasks shall be able to be run in batch mode as well as interative
+mode. In batch mode use of a graphics terminal or image display shall not
+be required.
+.le
+.ls (9)
+The DAOPHOT package shall be written in the SPP language in conformance with
+the standards and conventions of IRAF. The code shall be portable and
+device independent.
+.le
+.le
+.sh
+2.1 Limitations of the Initial DAOPHOT Package
+
+The DAOPHOT package shall perform PSF fitting photometry with the following
+restrictions:
+.ls
+.ls (1)
+The PSF used will be determined empirically and analytic specification of
+the PSF will not be possible. This restricts the use of DAOPHOT to image 
+data which is not too badly undersampled.
+.le
+.ls (2)
+There will be an upper limit to the number of stars for which the PSF will
+be fit simultaneously. The initial version of DAOPHOT will have this limit
+set to 60 stars.
+.le
+.ls (3)
+The initial version of DAOPHOT will not have the sky included as a parameter
+in the fitting routines. 
+.le
+.ls (4)
+Initially the use will not be able to mask out bad portions of the PSF for
+fitting.
+.le
+.le
+
+.sh
+3. Specifications
+
+     The DAOPHOT package performs stellar photometry on digital data, maintained
+as IRAF image files. DAOPHOT performs this photometry by fitting the PSF
+to the stellar images in the image file. DAOPHOT works by fitting the PSF to 
+a maximum number of stars simultaneously thus allowing for overlapping images.
+Input to the package consists of an imagefile and the output from the APPHOT
+package, which contains simple aperture photometry for the objects which have
+been identified in the image frame, and numerous parameters controlling the
+analysis algorithms. Output from the analysis tasks consists of tabular data
+containing the results of the analysis routines. The output will be in the
+form of SDAS tables and will thus be able to be manipulated by various
+other utility tasks available in IRAF.
+
+The CL callable part of the DAOPHOT package consists of the following routines:
+
+.ks
+.nf
+	addstar	  -- adds synthetic stars to an image file
+	allstar   -- fits multiple, overlapping PSFs to star images
+	*calibrate -- apply photometric calibration
+	*cmd	  -- color-magnitude, color-color diagrams
+	daopars    -- DAOPHOT pset parameters
+	examine   -- interactively examine/edit photometry results
+ 	group     -- divides stars into natural groupings
+	*growth    -- aperture growth curves <--> PSF magnitudes
+	peak      -- fit PSF to single stars in an image file
+	psf       -- interactively construct a PSF for the frame
+	nstar     -- fits multiple, overlapping PSFs to star images
+	seepsf	  -- converts a PSF file into a IRAF image file
+	select    -- selects natural groups with a certain range of sizes
+	substar   -- subtract fitted profiles from an image file
+.fi
+.ke
+
+There are routines available in other IRAF/STSDAS tasks for manipulating 
+SDAS Tables or DBIO. The capabilities inside the DAOPHOT are specifically 
+suited to dealing with large tables of results from these photometry routines. 
+
+.sh
+3.1 Standard Analysis Procedures
+
+     Before performing DAOPHOT photometry one must perform certain other tasks
+beforehand. This includes using the APPHOT package to produce an object list
+and aperture photometry for objects in this list. The DAOPHOT package contains
+an additional object finder but one must use APPHOT to obtain the aperture
+photometry results. The standard analysis procedure, including APPHOT, is as
+follows:
+.ls
+.ls (1)
+Use an object finder to produce a list of object coordinates. This may be done
+in many ways:
+.ls
+.ls o
+By using the interactive cusrsor routines available elsewhere in IRAF and
+redirecting the output into a list file.
+.le
+.ls o
+By transforming an existing list using an existing IRAF task or the OFFSET
+task in the DAOPHOT package.
+.le
+.ls o
+By using an automatic object finding procedure such as the one available
+in the APPHOT package or the one in the DAOPHOT package.
+.le
+.ls o
+By any other program which generates a list of objects in suitable format (SDAS
+Tables) for input to the APPHOT routines.
+.le
+.le
+.ls (2)
+The APPHOT package is run to measure the objects identified in the above
+step. One should refer to the APPHOT documentation to understand the
+algorithms and procedures which are used in APPHOT.
+.le
+.ls (3)
+One needs to set up the parameters in the analysis routines for this particular
+image file. OPTIONS allows you to set such parameters as the number of 
+electrons/ADC, the fitting radius, and the radius within which the PSF 
+is defined.
+.le
+.ls (4)
+The next step is to produce a PSF for the image file currently being processed.
+In crowed fields this is a tricky, iterative procedure which should be done very
+carefully. This is best done using a graphics terminal and/or an image display
+device.
+.le
+.ls (5)
+If one plans on using NSTAR, then the GROUP task must be run. This task 
+divides the stars in the output from the APPHOT into natural groups. The size
+of the groups produced depends upon how crowded the field is and what degree of
+overlap of the images one considers.
+.le
+.ls (6) 
+Use either NSTAR, if you have grouped the objects using GROUP, or 
+ALLSTAR which will dynamically group the stars as the image file is 
+processed. These routines will produce the objects' positions and 
+intrumental magnitudes by means of multiple-profile fits.
+.le
+.ls (7)
+Use SUBSTAR to subtract the fitted profiles from the image file, thus producing
+a new image file containing the fitting residuals. This will usually contain
+many stars which were missed in the original identification because they lie
+in the wings of brighter objects.
+.le
+.ls (8)
+One now basically runs through steps (1) - (6) one or more times, 
+merging the identified object lists each time to produce a master object list,
+until one is satisfied with the final results. There are many subtlties in this
+procedure which are described in the DAOPHOT User's Manual.
+.le
+.ls (9)
+After obtaining the photometry results one may edit the results by throwing out
+those results which do not meet certain criteria. EXAMINE is an interactive
+task which allows the user to examine the results for each individual object
+in the list and either accept or reject that object. There are also routines
+available for courser rejection of results, e.g. reject all objects with
+errors larger than 0.2 magnitudes.
+.le
+.ls (10)
+One may wish to use the tasks to plot up color-color or color-magnitude
+diagrams. Other general purpose list processing tools available in
+IRAF/SDAS may also be used for analysis of DAOPHOT output.
+.le
+.le
+
+.sh 
+3.2 The ADDSTAR Task
+
+     The function of ADDSTAR is to add synthetic stars to the image file.
+These stars may be placed randomly by the computer, placed with a certain
+distribution as specifed by the user or at predetermined locations specified
+by the user. Likewise the brightness of these added objects may be completely
+random or may follow a specified distribution. 
+
+Objects are added by taking the specified PSF, scaling it, and moving it
+to the desired location. ADDSTAR will also add Poisson noise to the star
+images to make them more realistic.
+
+.sh
+3.2.1 ADDSTAR Parameters
+
+     ADDSTAR has several parameters which control the addition of stars
+into a image file. All data dependent parameters are query mode to ensure
+that they get set properly for the particular image under consideration.
+The data independent parameters are hidden mode, and are given reasonable
+default values. The names, datatypes, and default values of the ADDSTAR
+parameters are shown below.
+
+.ks
+.nf
+Positional or query mode parameters:
+
+	input_image	filename
+	output_image	filename
+	minmag		real
+	maxmag		real
+.fi
+.ke
+
+.ks
+.nf
+List structured parameter (filename may be given on command line):
+
+	add_data	*imcur
+.fi
+.ke
+
+.ks
+.nf
+Hidden Parameters:
+
+	daopars		pset		"daophot$daopars.par"
+	nstar		integer		100
+	nframe		integer		1
+	xmin		integer		1
+	ymin		integer		1
+	xmax		integer		NX
+	ymax		integer		NY
+	verbose		boolean		false
+.fi
+.ke
+
+The function and format of each of these parameters is explained in
+more detail below.
+
+.ls
+.ls 16 input_image
+The name of the image or image section to which artificial stars will be added
+.le
+.ls output_image
+The name of outout image which will contain the added stars.
+.le
+.ls minmag
+The minumum magnitude of artificial star to add to the data. The magnitude
+scale is set by the magnitude of the PSF.
+.le
+.ls maxmag
+The maximum magnitude of artificial star to add to the data. The magnitude
+scale is set by the magnitude of the PSF.
+.le
+.ls add_data
+This parameter is used to specify a file as input to the ADDSTAR task. This
+file should contain centroid positions and magnitudes for the stars you 
+want to add. It is possible to specify the positions of the added stars
+interactively with the image display by setting this parameter to *imcur.
+In this case the user is prompted for the magnitude of each star to be added.
+If this parameter is the null string then the stars are added in a random
+fashion by the ADDSTAR routine.
+.le
+.ls nstar
+The number of artificial stars to add to the input image file.
+.le
+.ls daopars
+This is the name of a file containing parameters which are common to
+many DAOPHOT tasks. This pset parameter serves as a pointer to the external
+parameter set for the DAOPHOT algorithms. The parameters contained in this
+pset and their function are described in section 3.6.1.
+.le
+.ls nframe
+The number of new image files to create. If this parameter is greater
+than one then the new image files will use the output image name as
+a root and produce image files with '.xxx' appended to the root, where
+xxx will range from 001 to nframe. If nframe is one then the output image
+name will be used as is.
+.le
+.ls xmin, ymin, xmax, ymax
+These define the subsection of the image in which to add the artificial
+stars. The default is to add artificial stars to the complete image.
+.le
+.ls verbose
+Controls the amount of output from the ALLSTAR function. The default is
+to have minimal output to STDOUT.
+.le
+.le
+
+.sh
+3.2.2 ADDSTAR Output
+
+     The output of ADDSTAR consists of two parts, an image file and an
+output SDAS Table. The image file is a copy of the input image file but
+with the artificial stars generated by ADDSTAR added. The output table
+contains the x,y position and magnitude of each of the added stars. When the
+nframe parameter is set greater than one then there will be nframe pairs of
+output files generated.
+
+.sh
+3.3 ALLSTAR
+
+     ALLSTAR fits multiple, overlapping point-spread functions to stars images
+in the input image file. It uses as input the results from APPHOT and an
+input PSF and will automatically reduce the entire image performing the necessary
+grouping. It will recalculate the grouping after each iteration. ALLSTAR will
+also produce the star-subtracted image file.
+
+.sh
+3.3.1 ALLSTAR Parameters
+
+ALLSTAR has several parameters which control the fitting algorithms. The 
+names, datatypes, default values for the ALLSTAR parameters are given below.
+
+.ks
+.nf
+Positional parameters:
+
+	input_image	filename
+	photometry	filename
+	output		filename
+	sub_image	filename
+.fi
+.ke
+
+.ks
+.nf
+Hidden parameters:
+
+	daopars		pset		"daophot$daopars.par"
+	max_group	integer		60
+	redeterm_cent	boolean		true
+	max_crit	real		2.5
+	min_crit	real		1.2
+	clip_exp	integer		6
+	clip_range	real		2.5
+	verbose		boolean		false
+.fi
+.ke
+
+These parameters perform the following functions:
+
+.ls 4
+.ls 16 input_image
+The name of the input image file.
+.le
+.ls photometry
+The name of the input photometry SDAS table. This may contain output from either
+the APPHOT package or from NSTAR or previous ALLSTAR runs.
+.le
+.ls output
+The name of the SDAS table to contain the results of the psf fittting.
+.le
+.ls sub_image
+The name of the output image file which will have all of the fitted stars
+subtracted from it. If this file is the null string then no star-subtracted
+image file will be produced.
+.le
+.ls daopars
+The pset parameter file containing the DAOPHOT parameter set.
+.le
+.ls max_group
+The maximum size group which ALLSTAR will process. The absolute maximum
+is 60 stars.
+.le
+.ls redeterm_cent
+If true then the centers of the stars are redetermined before each 
+iteration.
+.le
+.ls max_crit
+The initial value which ALLSTAR uses as the critical separation for
+use in grouping stars together. For groups larger than "max_group" ALLSTAR
+will use progressively smaller values for the critical separation until  the
+group breaks up into units containing fewer than "max_group" stars or until
+the value of "min_crit" is reached.
+.le
+.ls min_crit
+The smallest value of the critical separation which ALLSTAR will use in
+grouping stars together.
+.le
+.ls clip_exp, clip_range
+These parameters are used to "resist bad data". These two 
+parameters control the weighting of each pixel as a function of it's
+residual from the fit. Clip_range us variable "a" and clip_exp is
+variable "b" in the paper by Stetson (P.A.S.P. 99, 191)
+.le
+.le
+
+.sh
+3.3.2 The ALLSTAR PSF Fitting Algorithm
+
+     The algorithms which ALLSTAR uses to do the psf fitting photometry are 
+very nearly the same as those used by NSTAR. One is referred to Stetson,
+P.A.S.P. 99, 191, for the details on the various fitting, star rejection,
+and weighting algorithms used in this task.
+.sh
+3.3.3 The Output from ALLSTAR
+
+     The output from ALLSTAR consists of three parts. There is the output
+photometry results, an SDAS Table, and a subtracted image file. The subtracted
+image file is a copy of the input image file minus the fitted stars.
+
+For each object processed by ALLSTAR there is one row in the output SDAS
+Table. Each measured object will have entries for the following items:
+
+.nf
+     star, x, y, mag, magerr, sky, niter, chi, sharp
+
+where
+
+     star	star ID number
+     x,y	coordinates of the stellar centroid
+     mag	magnitude relative to the magnitude of the PSF star
+     magerr	estimated standard error of the star's magnitude
+     sky	estimated sky as returned by APPHOT
+     niter	number of iterations for convergence
+     chi	observed pixel to pixel scatter DIVIDED BY the expected
+                pixel to pixel scatter
+     sharp	an index describing the spatial distribution of the residuals
+                around the star. Objects with SHARP significantly greater
+                than zero are extended (possibly galaxies), while objects with
+                SHARP significantly less than zero may be bad pixels or cosmic
+                rays
+.fi
+
+Other noteworthy pieces of information will be stored in the output SDAS
+Table header. This includes such things as the time and date of processing,
+the name of the PSF file, the name of the input photometry file, the
+fitting radius etc.
+
+.sh 
+3.4 The CALIBRATE Task
+
+.sh 
+3.5 The CMD Task
+
+.sh 
+3.6 The DAOPARS Task
+
+     This is a pset-task which is used to describe a particular image file
+for use with the DAOPHOT package. This pset contains parameters which describe the
+data, e.g. the read out noise, the background sky value, the number of photons
+per ADC unit, etc., and also parameters which control the DAOPHOT tasks, e.g.
+the fitting radius to use. The parameters in this pset are used by several
+DAOPHOT tasks, hence their grouping into a pset.
+
+.sh
+3.6.1 daopars Parameters
+
+     The parameters in this task either describe the data in
+a particular image file
+or are parameters which are used by more algorithms in more than one
+DAOPHOT task. The following parameters make up this pset:
+
+.ks
+.nf
+
+	fitrad		real		2.5 (pixels)
+	psfrad		real		11.0(pixels)
+	phot_adc	real		10.0
+	read_noise	real		20.0
+	max_good	real		32766.
+	min_good	real		0.0
+	sky_val		real		0.0
+	numb_exp	integer		1
+	comb_type	string		"average"
+	var_psf		boolean		false
+.fi
+.ke
+
+The function and format of each of these parameters is described below:
+
+.ls 4
+.ls 16 fitrad
+The fitting radius to use in the PEAK, NSTAR, ALLSTAR and PSF tasks. Only
+the pixels within one fitting radius are actually used in the fit. This should
+normally be on the order of the FWHM of the stellar images.
+.le
+.ls psfrad
+The radius of the circle within which the PSF is defined. This should be 
+somewhat larger than the actual radius of the brightest star you are 
+interested in.
+.le
+.ls maxgood
+The maximum data value in ADC units at which the CCD or other detector
+is believed to operate linearly.
+.le
+.ls mingood
+The minimum data value in ADC units which should be used as "real" data.
+Dead pixels, bad columns etc. in the image file can be excluded from use in 
+the analysis by setting this parameters properly. Any data value which
+falls below this minimum is ignored by DAOPHOT tasks.
+.le
+.ls sky_val
+The typical sky brightness in ADC units for the image file. This parameter is
+updated by the SKY task within the  DAOPHOT package.
+.le
+.ls phot_adc
+The number of photons per ADC unit of the CCD or other detector.
+.le
+.ls read_noise
+The readout noise in ADC units of the CCD or other detector.
+.le
+.ls numb_exp
+The number of individual exposures which have been combined to produce the
+current image file. This number combined with information on whether the
+exposures were summed or averaged is used to get a better handle on the
+error estimates of the photometry.
+.le
+.ls comb_type
+Describes whether the individual exposures which went into making up this
+image file were "summed" or "averaged"
+.le
+.ls var_psf
+Controls whether the shape of the PSF is to be regarded as constant over the
+complete image file. Slight and smooth variations can be accomodated by the
+DAOPHOT tasks.
+.le
+.le
+
+     These parameters should be initially set by the user before starting any
+analysis with the DAOPHOT package. Each image file may have it's own set of
+parameters and these should be stored in separate pset files. 
+.sh 
+3.7 The EXAMINE Task
+
+     EXAMINE allows the user to interactively examine the results of the
+DAOPHOT reduction and to accept or reject individual stars. EXAMINE will
+accept as input the output photometry list from either ALLSTAR or NSTAR.
+For each star in the input list the user can examine either a 3-d meshplot
+or a contour diagram of both the input image and the star-subtracted image.
+The results of the photometry for the star under consideration is also
+displayed.
+
+Two output star lists are produced using this task. One is a list
+of stars which have been "accepted" by the user, the other being a list
+of stars which have been "rejected".
+
+If the TV option is selected then both the original image and subtracted 
+image are displayed on the "stdimage" and the star under consideration is
+identified. The user has the ability to blink these two frames to
+evaluate the results of the photometry.
+
+This task is controlled via input from the terminal with various keys 
+performing a variety of functions.
+
+.sh
+3.7.1 EXAMINE Parameters
+     There are several parameters which control various aspects of the
+EXAMINE task. The parameters control such things as the input photometry
+list, the type of graphical display desired and whether to use the
+display capabilities.
+
+.ks
+.nf
+Query mode parameters:
+
+	phot_list		filename
+
+	fwhm			real (pixels)
+	threshold		real (in units of sigma)
+	output_file		filename
+.fi
+.ke
+
+.sh 
+3.9 The GROUP Task
+
+     GROUP is used to divide the stars in the image file into natural
+groups prior to analysis with NSTAR. GROUP works on the following
+principle: if two stars are close enough that the light of one will
+influence the profile fit of the other, then they belong in the same
+group.
+
+.sh
+3.9.1 GROUP Parameters
+
+     GROUP only has a few parameters which govern its operation. These
+are:
+
+.ks
+.nf
+Query mode parameters:
+
+	input_image		filename
+	psf_file		filename
+	crit_overlap		real
+	output			filename
+.fi
+.ke
+
+.ks
+.nf
+Hidden mode parameters:
+
+	daopars		pset	"daophot$daopars.par"
+.fi
+.ke
+
+These parameters perform the following functions:
+
+.ls 4
+.ls 16 input_image
+The name of the input image file.
+.le
+.ls psf_file
+The name of the file containing the PSF.
+.le
+.ls crit_overlap
+The "critical overlap" before one star is determined to influence 
+another. When GROUP examines two stars to see whether they might influence
+each others' fits, it firts identifies the fainter of the two stars. It then
+calculates the brightness of the brighter star at a distanceof one fitting
+radius plus one pixel from the center of the fainter. If this brightness is
+greater than the "critical overlap" times the random error per pixel, then
+the brighter star is deemed to be capable of affecting the photometry of the 
+fainter, and the two stars are grouped together.
+.le
+.ls output
+The name of the SDAS table which will contain the stellar groups.
+.le
+.ls daopars
+The name of of a pset file containing the daophot parameters. The specific
+parameters which are used from this include the following:
+.le
+.le
+.sh 
+3.10 The GROWTH Task
+
+.sh 
+3.11 The OFFSET task
+
+.sh 
+3.12 The PEAK Task
+
+     PEAK fits the PSF to a single star. It is useful for sparsely populated 
+image files where the stars of interest are not blended. In this cases aperture
+photometry is often fine and the use of PEAK is of limited interest. This task
+is included in the DAOPHOT package mainly for completeness.
+
+.sh
+3.12.1 PEAK Parameters
+
+     The parameters specific to the PEAK task are used for specifying the
+input and output from this routine. The names of the parameters and their
+functions are:
+
+.ks
+.nf
+Positional or query parameters:
+
+	input_image		filename
+	psf_file		filename
+	output			filename
+.fi
+.ke
+
+.ks
+.nf
+Hidden parameters:
+
+	daopars		pset	"daophot$daopars.par"
+	verbose		boolean false
+.fi
+.ke
+
+.ls 4
+.ls 16 input_image
+The name of the input image file.
+.le
+.ls psf_file
+The name of the input file containing the point-spread function.
+.le
+.ls output
+The name of the SDAS table to contain the output from PEAK.
+.le
+.ls verbose
+If true then PEAK outputs more information about what it is doing.
+.le
+.ls daopars
+The name of a pset file which contains the parameters specific to the
+input image file. The parameters which PEAK uses from this pset include:
+sthe fitting radius, the maximum and minimum good data value and whether
+a variable PSF is to be used.
+.le
+.le
+.sh 
+3.13 The PSF Task
+
+     The PSF task is used for obtaining the point-spread function which
+will be used in the rest of the DAOPHOT reductions. DAOPHOT uses an
+empirical point-spread function as opposed to a mathematically defined
+function. The PSF is defined from the actual brightness distribution
+of one or more stars in the frame under consideration. It is stored as
+a two-component model: (1) an analytic Gaussian profile which approximately
+matches the core of the point-spread function, and (2) a look-up table of
+residuals, which are used as additive corrections to the integrated 
+analytic Gaussian function.
+
+The brightness in a hypothetical pixel at an arbitrary point within the
+point-spread function is determined in the following manner. First
+the bivariate Gaussian function is integrated over the area of the pixel,
+and then a correction is determined by double cubic interpolation
+within the lookup table, and is added to the integrated intensity.
+
+The PSF is stored as a binary data file and is in a format specific
+to DAOPHOT. The format of this file is very similar to that used by the
+VMS version of DAOPHOT but is stored in binary for compactness.
+A function is provided to take the PSF and convert it
+to a IRAF image file so that it can be manipulated by other IRAF 
+tasks. 
+
+PSF allows the user to perform most functions from within the interactive
+graphics part of its operation. PSF allows the user to modify the 
+perspective of hist mesh plot, the contouring interval, the PSF radius 
+etc. from within the PSF interactive graphics. 
+
+.sh
+3.13.1 PSF Parameters
+
+     The PSF task has many parameters which specify the input and
+output files as well as specifying other information. These are
+divided in query mode parameters and hidden parameters.
+
+.ks
+.nf
+Positional or query parameters:
+
+	input_image		filename
+	phot_list		filename
+	psf_stars		filename
+	psf_file		filename
+.fi
+.ke
+
+.ks
+.nf
+Hidden parameters:
+
+	daopars		pset	"daophot$daopars.par"
+	verbose		boolean false
+.fi
+.ke
+
+.ls 4
+.ls 16 input_image
+The name of the input image file.
+.le
+.ls phot_list
+The name of the input file containing the aperture photometry
+results for this image frame.
+.le
+.ls psf_stars
+The name of file coordinate file containing the list of stars
+to be used as PSF candidates.
+.le
+.ls psf_file
+The name of the output file for storing the PSF.
+.le
+.ls verbose
+If true then PEAK outputs more information about what it is doing.
+.le
+.ls daopars
+The name of a pset file which contains the parameters specific to the
+input image file. The parameters which PEAK uses from this pset include:
+sthe fitting radius, the maximum and minimum good data value and whether
+a variable PSF is to be used.
+.le
+.le
+.sh 
+3.14 The NSTAR Task
+
+     NSTAR is one of DAOPHOT's multiple, simultaneous, profile-fitting
+photometry routine. It is similar to ALLSTAR except that NSTAR must have
+the objects grouped (using the GROUP task) and it does not dynamically
+alter the groups while running. NSTAR also does not automatically produce the
+star subtracted image file.
+
+.sh
+3.14.1 NSTAR Parameters
+
+     There are several parameters which control the function of the 
+NSTAR task. These are the following:
+
+.ks
+.nf
+Positional or Query Parameters:
+
+	input_image		filename
+	psf_file		filename
+	group_file		filename
+	output_file		filename
+.fi
+.ke
+
+.ks
+.nf
+Hidden parameters:
+
+	daopars		pset	"daophot$daopars.par"
+	verbose		boolean	false
+.fi
+.ke
+
+.sh 
+3.15 The SEEPSF Task
+
+     The SEEPSF task produces an IRAF image file from the given PSF
+file. This allows other IRAF tasks, especially display and plotting tasks,
+to use access the point-spread function. The user has the ability to create
+any size of image from the PSF enlargements being handled by a number of
+different interpolation schemes.
+
+.sh
+3.15.1 SEEPSF Parameters
+     
+     The parameters wich control this task are limted. They basically
+control the input, output and size of the image.
+
+.ks
+.nf
+Positional or Query Parameters:
+
+	psf_file		filename
+	image_name		filename
+	image_size		integer
+.fi
+.ke
+
+.ks
+.nf
+Hidden parameters:
+
+	interpolation	string  "nearest"
+	boundary	string	"constant"
+	constant	real	0.0
+	daopars		pset	"daophot$daopars.par"
+	verbose		boolean false
+.fi
+.ke
+
+.ls 4
+.ls 16 psf_file
+This specifies the input PSF file which is to be transformed into an
+IRAF image.
+.le
+.ls image_name
+The name of the output IRAF image.
+.le
+.ls image_size
+The size of the output image in pixels per side. Note that only square PSFs
+and PSF images are alllowed.
+.le
+.ls interpolation
+The type of interpolation to be used in expanding the image. The choices
+are "nearest" neighbor, "linear" bilinear, "poly3" bicubic polynomial,
+"poly5" biquintic polynomial, and "spline3" bicubic spline.
+.le
+.ls boundary
+The type of boundary extension to use for handling references to pixels
+outside the bounds of the input image. The choices are: "constant",
+"nearest" edge, "reflect" about the boundary and "wrap" to the other side
+of the image.
+.le
+.le
+.sh 
+3.16 The SELECT Task
+
+     The SELECT task is used to select groups of stars with a particular
+range of sizes from a group file which has been produced by GROUP. This 
+task is used when some of the groups in the group file are large than the
+maximum allowed in NSTAR, currently 60 stars. 
+
+.sh
+3.16.1 SELECT Parameters
+
+     The parameters which control the SELECT task are the following:
+
+.ks
+.nf
+Positional or Query Parameters:
+
+	input_group		filename
+    	output_group		filename
+	min_group		integer
+	max_group		integer
+.fi
+.ke
+
+.le 4
+.ls 16 input_group
+The input group file which is to be searched for groups within the
+limits specified by min_group and max_group.
+.le
+.ls output_group
+The output group file which will consist of groups between 'min_group'
+and 'max_group' in size.
+.le
+.ls min_group
+The minimum group size to be extracted from the input group file.
+.le
+.ls max_group
+The maximum group size to be extracted from the input group file.
+.le
+.le
+.sh 
+3.17 The SKY Task
+
+.sh 
+3.18 The SORT Task
+
+.sh 
+3.19 The SUBSTAR Task
+
+     The SUBSTAR command takes the point-spread function for an image
+frame and a file containing the x,y coordinates and apparent magnitudes
+for a group of stars, usually an output file from one of the photometry
+routines, shifts and scales the PSF function 
+according to each position and magnitude, and then subtracts it from the 
+original image frame. 
+
+.sh
+3.19.1 SUBSTAR Parameters
+
+     The parameters for SUBSTAR control the input and output from this 
+task.
+
+.ks
+.nf
+Positional or Query Parameters:
+
+	psf_file		filename
+	phot_file		filename
+	input_image		filename
+	output_image		filename
+.fi
+.ke
+
+.ks
+.nf
+Hidden parameters:
+
+	verbose		boolean false
+.fi
+.ke
+
+.ls 4
+.ls 16 psf_file
+The name of the file containing the PSF which is to be used as the template 
+in the star subtraction.
+.le
+.ls phot_file
+The file containing the photometry results for the stars which are to be
+subtracted from the input image.
+.le
+.ls input_image
+The name of the input image file from which the stars are to be subtracted.
+.le
+.ls output_image
+The name of the output image file which will be a copy of the input frame
+except for the subtracted stars.
+.le
+.ls verbose
+If this parameter is set to true then more information about the progress
+of SUBSTAR is output.
+.le
+.le
+.sh 
+4.0 Example
+
+.endhelp
diff --git a/noao/digiphot/daophot/doc/specs/daoutils.spc b/noao/digiphot/daophot/doc/specs/daoutils.spc
new file mode 100644
index 00000000..d943d63a
--- /dev/null
+++ b/noao/digiphot/daophot/doc/specs/daoutils.spc
@@ -0,0 +1,700 @@
+.help daoutils Jan89 "Utility Package for DAOPHOT"
+.sh
+1. Introduction
+
+The DAOUTILS package will provide a set of tools for working
+with the output from DAOPHOT. These tools will provide the user with
+the ability to select data upon ranges and limits for any of the
+fields in a daophot output table. The package will also provide tools
+for merging results contained in different output files.
+
+.sh
+2. Requirements
+.ls 4
+.ls (1)
+The tasks in the DAOUTILS package shall take as input the output ST Tables
+from the DAOPHOT tasks. The convert task in the daophot package shall be
+used to convert the output from apphot tasks into the proper format for use
+with the daoutils package.
+.le
+.ls (2)
+The tasks in the package which produce tabular output shall use the
+ST Tables for their output and those tasks which read output from other
+DAOUTILS tasks will be able to read ST Tables. 
+.le
+.ls (3)
+The DAOUTILS  package shall include tasks to inspect and edit the results 
+from the photometry routines. These shall include tasks such as interactively
+rejecting particular stars from the results, 
+producing plots of errors versus brightness, errors versus position etc. There
+will also be a task for merging the results contained in several different
+Tables. It shall also be possible to interactively examine the photometry
+results with various graphical and/or display tools for inspecting/editing the
+results. It shall also be possible to construct growth curves from the
+aperture photometry for the purpose of calibrating  the daophot magnitudes
+to total magnitudes. There shall also be routines for calibrating the
+photometry by the use of standard stars.
+.le
+.ls (4) 
+The tasks shall be able to be run in batch mode as well as interative
+mode. In batch mode use of a graphics terminal or image display shall not
+be required.
+.le
+.ls (5)
+The DAOPHOT package shall be written in the SPP language in conformance with
+the standards and conventions of IRAF. The code shall be portable and
+device independent.
+.le
+.le
+.sh
+2.1 Limitations of the Initial DAOUTILS Package
+
+The DAOUTILS package will have the following limitations:
+.ls
+.ls (1)
+The initial version of DAOUTILS will not make direct use of the interactive
+image display. It will make use of cursor readback however.
+.le
+.le
+
+.sh
+3. Specifications
+
+The DAOUTILS package will take the output from the DAOPOHT package as input
+and provide a variety of tools which will allow the use to examine, edit and
+calibrate the output from DAOPHOT. The output from DAOUTILS will consist of
+ST Tables, graphical displays and printed summaries.
+
+The CL callable part of the DAOUTILS package will consist of the following 
+tasks:
+
+.ks
+.nf
+	merge     -- Merge the results from different runs of daophot
+	daograph  -- Graph the results of daophot stored in ST Tables
+	gtedit     -- Interactive graphical data editor
+	examine   -- Interactively examine the output from daophot
+	growth    -- aperture growth curves <--> PSF magnitudes
+	cmd       -- Color-magnitude and color-color plots
+	calibrate -- do photometric calibration
+
+.fi
+.ke
+
+In addition the ttools package provided as part of STSDAS provides for
+many generic tools for working with the ST Tables are will be usable for
+many of the data selection tasks which most users will wish to apply to 
+daophot output.
+
+.sh
+3.1 The GTEDIT Task
+
+The user will be able to plot any two columns of a Table versus each other
+and with the cursor interactively delete records. The user will move the
+graphics cursor near the point on the graph which represents the record
+which he wishes to delete from the input record. The user will also be able
+to specify 'areas' of the plot for which all records pointed to by points
+in the indicated sections will be deleted. The user will also be
+able to undelete records. The records will not actually be deleted until the
+task ends. The user will also be able to interactively change which columns 
+are being plotted versus each other. The user will also have the option of
+editing the table in place or to create a new output table which will contain
+the edited results of the input table.
+
+.sh
+3.1.1 GEDIT Parameters
+
+GEDIT will have input parameters which control the input and initial
+operation of the task.
+
+.ks
+.nf
+Positional or query mode parameters:
+
+	input	- filename
+	xcolumn - column name (string)
+	ycolumn - column name (string)
+.fi
+.ke
+
+.ks
+.nf
+Hidden parameters:
+
+	inplace 	boolean		"false"
+	output  	filename	""
+	reject		filename	""
+.fi
+.ke
+
+The function and format of these parameters is decsribed in more detail
+below.
+
+.ls
+.ls 16 input
+The name of the input table which contains the output from DAOPHOT.
+.le
+.ls xcolumn
+The name of the column in the input table which will be used for the
+X axis of the plot
+.le
+.ls ycolumn
+The name of the column in the input table which will be used for the
+Y axis of the plot
+.le
+.ls inplace
+Controls whether the input table is modified in place or whether a new 
+table is created.
+.le
+.ls output
+If inplace is false then the value of this parameter will be the name of
+the output table which will contain the edited output.
+.le
+.ls reject
+The name of the output file containing those objects which have been
+deleted. If this parameter is NULL then the records which have been
+deleted are not saved.
+.le
+.le
+
+.sh
+3.1.2 Interactive GEDIT Commands
+
+Once GEDIT has plotted the two columns specified as the input there are
+several commands available to the user. These allow the user to delete/undelete
+points, change which columns are plotted, view a particular record from the
+input table and exit GEDIT.
+
+.ks
+.nf
+In the interactive mode the following cursor keys are active:
+
+	x  -- delete the record represented by the point nearest the cursor
+	>  -- delete all records represented by Y values > than the cursor
+	<  -- delete all records represented by Y values < than the cursor
+	+  -- delete all records represented by X values > than the cursor
+	-  -- delete all records represented by X values < than the cursor
+	b  -- mark the corner of box containing records to be deleted.
+	u  -- undelete the record(s) deleted by the last delete operation
+	q  -- exit GEDIT
+.fi
+.ke
+
+.ks
+.nf
+In addition the following colon commands are available:
+
+	:xcol <name>  Use the column <name> as the X axis
+	:ycol <name>  Use the column <name> as the Y axis
+.fi
+.ke
+
+.sh
+3.1.3 GEDIT OUTPUT
+
+The output from GEDIT is a direct copy of the input table with the records
+which the user marked for deletion removed. If the parameter 'inplace' was
+set to true then the edited table replaces the original table, otherwise a
+new table is created. Is it important that no records be deleted until the 
+user exits GEDIT and confirms that the update is to take place.
+
+.sh
+3.2 TGRAPH
+
+This task is will produce plots from the DAOPHOT output tables. It is similar
+to the sgraph task in STSDAS but does not have the option of plotting image 
+sections. It does have the ability to plot error bars and columns of data from
+two different tables.
+
+The following is the help for sgraph:
+
+.ih
+NAME
+graph -- graph one or more lists, image sections, or tables
+.ih
+USAGE
+graph input
+.ih
+PARAMETERS
+.ls input
+List of operands to be graphed.  May be STDIN, or one or more image
+sections, tables and columns, or lists.  SDAS table input is specified
+by:  a table name and column name, a table and two column names, or a
+pair of table and column names, separated by white space. 
+.le
+.ls stack = no
+If stack = yes, plot multiple curves on separate axes (WCS) stacked 
+vertically rather than on the same axes.
+.le
+.ls wx1=0., wx2=0., wy1=0., wy2=0.
+The range of user coordinates spanned by the plot.  If the range of values
+in x or y = 0, the plot is automatically scaled from the minimum to
+maximum data value along the degenerate dimension.
+.le
+.ls vx1=0., vx2=0., vy1=0., vy2=0.
+NDC coordinates (0-1) of the device plotting viewport.  If not set by 
+the user, a suitable viewport which allows sufficient room for all labels 
+is used.
+.le
+.ls pointmode = no
+If \fBpointmode\fR = yes, plot points or markers at data values, rather than 
+connected lines.
+.le
+.ls marker = "box"
+Marker to be drawn if \fBpointmode\fR = yes.  Markers are "point", "box", 
+"cross", "plus" or "circle".
+.le
+.ls szmarker = 0.005
+The size of a marker in NDC coordinates (0 to 1 spans the screen).
+If zero and the input operand is a list, marker sizes are taken individually
+from the third column of each list element.  If positive, all markers are
+of size \fBszmarker\fR.  If negative and the input operand is a list,
+the size of a marker is the third column of each list element times the
+absolute value of \fBszmarker\fR.
+.le
+.ls xlabel = "", ylabel = ""
+Label for the X-axis or Y-axis.
+.le
+.ls title = "imtitle"
+Plot title.  If \fBtitle\fR  = "imtitle"
+and the first operand in \fBinput\fR is an image, the image title is used
+as the plot title.
+.le
+.ls box = yes
+Draw axes at the perimeter of the plotting window.
+.le
+.ls fill = yes
+Fill the output viewport regardless of the device aspect ratio?
+.le
+.ls axis = 1
+Axis along which the projection is to be computed, if an input operand is
+an image section of dimension 2 or higher.  Axis 1 is X (line average),
+2 is Y (column average), and so on.
+.le
+.ls erraxis = 0
+If pointmode = no and erraxis is 1 or 2, the axis parallel to which
+error bars are plotted (1 ==> X, 2 ==> Y). 
+.le
+.ls errcolumn = ""
+The column(s) in the input table to be used as the error amplitude(s).
+If one column name, then symmetrical symmetrical error bars are drawn,
+centered on the data points with the total size, in WC specified by the
+values in the column from the same table specified in parameter input.
+Two names specify two table columns for the lower and upper errors,
+respectively. 
+.le
+.ls pattern = "solid"
+The line pattern for the first curve.  Subsequent curves on the same 
+plot cycle through the set of patterns:  solid, dashed, dotted, dotdash.
+.le
+.ls crvstyle = "straight"
+The style of the plotted curve:  "straight" is the usual straight 
+line connection between points, "pseudohist" consists of horizontal 
+segments at each data point connected by vertical segments, "fullhist" 
+is a bar graph or histogram style plot.
+.le
+.ls transpose = no
+Swap the X and Y axes of the plot.  If enabled, the axes are transposed 
+after the optional linear transformation of the X-axis.
+.le
+.ls xflip = no, yflip = no
+Flip the axis?  That is, plot and label X values increasing right to
+left instead of left to right and/or Y values top to bottom instead of
+bottom to top. 
+.le
+.ls logx = no, logy = no
+Log scale the X or Y axis.  Zero or negative values are indefinite and
+will not be plotted, but are tolerated.
+.le
+.ls ticklabels = yes
+Label the tick marks.
+.le
+.ls majrx=5, minrx=5, majry=5, minry=5
+Number of major tick marks on each axis; number of minor tick marks between
+major tick marks.  Ignored if log scaling is in effect for an axis.
+.le
+.ls lintran = no
+Perform a linear transformation of the X-axis upon input.  Used to assign
+logical coordinates to the indices of pixel data arrays (image sections).
+.le
+.ls p1=0, p2=0, q1=0, q2=1
+If \fBlintran\fR is enabled, pixel index P1 is mapped to Q1, and P2 to Q2.
+If P1 and P2 are zero, P1 is set to 1 and P2 to the number of pixels in
+the input array.
+.le
+.ls round = no
+Extend the axes up to "nice" values.
+.le
+.ls append = no
+Append to an existing plot.  
+.le
+.ls device = "stdgraph"
+The output device.
+.le
+.ih
+DESCRIPTION
+\fBGraph\fR graphs one or more lists, image sections, or table columns;
+lists and image sections may be mixed in the input list at will.  If the
+curves are not all the same length the plot will be scaled to the
+longest curve and all curves will be plotted left justified.  If an
+image section operand has more than one dimension the projection
+(average) along a designated axis will be computed and plotted.  By
+default, a unique dash pattern is used for each curve, up to a maximum
+of 4. 
+
+List input may be taken from the standard input or from a file,
+and consists of a sequence of Y values, X and Y values, or X, Y,
+and marker size values, one pair of coordinates per line in the list.
+Blank lines, comment lines, and extra columns are ignored.
+The first element in the list determines whether the list is a Y list
+or and X,Y list; it is an error if an X,Y list has fewer than two
+coordinates in any element.  INDEF valued elements appear as gaps
+in the plot.
+
+SDAS table input is specified by a table name and column name, a table 
+and two columns, or a pair of table and column names separated by white 
+space.  The table name may be a file name template.  Note that this is a 
+single string, so that it must be quoted if entered on the command line.
+
+Error bars may be plotted for data from list or table input.  Errors may
+be in X or in Y and separate upper and lower errors may be specified. 
+If `pointmode' is "no" then the parameter `erraxis' specifies if the
+errors are in X or in Y if its value is 1 or 2, respectively.  If
+`pointmode' is "no" and `erraxis' is zero, a polyline is plotted (see 
+below).  If the input data come from a list, then the third (size)
+column specifies the amplitude of symmetrical error bars.  If there is a
+fourth column, the third and fourth columns specify the amplitudes of
+the lower and upper errors, respectively.  If the input data are in a
+table, the parameter `errcol' specifies the source of the errors. 
+If `errcol' contains a single word, it is the column in the same table
+as the input data containing the amplitudes of symmetrical errors.  If
+`errcol' contains two words, they specify the columns in the same table
+containing the amplitudes of the lower and upper errors, respectively.
+If the X and Y data come from different tables, then `erraxis' specifies
+which table contains the error column or columns.  Error data may not
+come from image data.  The `append' parameter may be used
+to overplot several curves of different style. 
+
+Different line types and curve styles may be selected.  The string
+parameter `crvstyle' may take on one of the values:  "none", "straight",
+"pseudohist", or "fullhist", specifying the style of connections between
+data points;  the string parameter `pattern' can take on one of the
+values "solid", "dashed", "dotted", "dotdash" to indicate the style
+of the first line drawn.  Subsequent lines drawn on the same graph cycle
+the available styles. 
+
+If \fBappend\fR is enabled, previous values for \fBbox\fR,
+\fBfill\fR, \fBround\fR, the plotting viewport (\fBvx1\fR, \fBvx2\fR, 
+\fBvy1\fR, \fBvy2\fR), and the plotting window (\fBwx1\fR, \fBwx2\fR, 
+\fBwy1\fR, \fBwy2\fR) are used.
+
+By default, the plot drawn will fill the device viewport, if the viewport
+was either specified by the user or automatically calculated by 
+\fIgraph\fR.  Setting
+the value of \fBfill\fR  to "no" means the viewport will be adjusted so 
+that equal numbers of data values in x and y will occupy equal lengths 
+when plotted.  That is, when \fBfill = no\fR, a unity aspect ratio is 
+enforced, and plots
+appear square regardless of the device aspect ratio.  On devices with non 
+square full device viewports (e.g., the vt640), a plot drawn by \fIgraph\fR
+appears extended in the x direction unless \fBfill\fR = no.
+
+.ih
+EXAMPLES
+Plot the output of a list processing filter:
+
+	cl> ... list_filter | graph
+
+Plot a graph entered interactively from the terminal:
+
+	cl> graph STDIN
+
+Overplot two lists:
+
+	cl> graph list1,list2
+
+Graph line 128 of image "pix":
+
+	cl> graph pix[*,128]
+
+Graph the average of columns 50 through 100:
+
+	cl> graph pix[50:100,*] axis=2
+
+Graph two columns from a table against each other:
+
+	cl> graph "table xcol ycol"
+
+Graph a list in point plot mode:
+
+	cl> graph list po+
+
+Annotate a graph:
+
+.nf
+	cl> graph pix[*,10],pix[*,20] xlabel=column\
+	>>> ylabel=intensity title="lines 10 and 20 of pix"
+.fi
+
+Direct the graph to the standard plotter device:
+
+	cl> graph list device=stdplot
+.ih
+BUGS
+Indefinites are not recognized when computing image projections.
+
+End sgraph help.
+
+.sh
+3.3 The MERGE Task
+
+This task will merge the results from a maximum of four DAOPHOT output
+files based upon positional coincidence. This task will work on files
+which could have been run images with different scales, orientations etc.
+MERGE will need to transform the coordinate systems of the input photometry
+lists to a common coordinate system. There will be two ways of inputing the
+transformations to be applied to the coordinate lists: 1) Simple X, Y shifts
+or 2) transformations as determined by the GEOMAP task. This will allow the
+most common cases to handled in a simple way without having to run the GEOMAP
+task.
+
+The user will be able to specify a match radius which will determine how
+close to each other two objects must be to be considered a coincidence.
+The user will also be able to specify the number of lists an object must
+be identified in to be included in the output file. For example, if the
+user was merging photometry results from four different output tables
+he could request that the output table would contain entries for matches
+between any two or more of the four tables. The output Table from MERGE
+will simply contain pointers to the corresponding rows of the various
+input tables and not contain a copy of the complete row from each table
+for those objects which were matched. The user will then run another task,
+MSELECT to select the fields he wants from the original photometry files.
+This will allow the user to select only the fields he wants and to do the
+selection more than once without remerging the individual files.
+
+.sh
+3.3.1 MERGE Parameters
+
+MERGE shall have parameters which control the input and functioning of the
+task.
+
+.ks
+.nf
+Positional or query parameters:
+
+	ptable1  -- Input photometry table #1
+	ptable2  -- Input photometry table #2
+	ptable3  -- Input photometry table #3
+	ptable4  -- Input photometry table #4
+	matchrad -- Matching radius for coincidence
+	nmatch   -- minimum number of matches to be included in output
+	merge_table -- output table containing merge pointers
+.fi
+.ke
+
+.ks
+.nf
+Hidden Parameters:
+
+	gmfile12  -- geomap database name for transforming #1 -> #2
+	gmrec12	  -- geomap database record for transforming #1 -> #2
+	gmfile13  -- geomap database name for transforming #1 -> #3
+	gmrec13	  -- geomap database record for transforming #1 -> #3
+	gmfile14  -- geomap database name for transforming #1 -> #4
+	gmrec14	  -- geomap database record for transforming #1 -> #4
+	dx12  -- X offset (x2 - x1)
+	dy12  -- Y offset (y2 - y1)
+	dx13  -- X offset (x3 - x1)
+	dy13  -- Y offset (y3 - y1)
+	dx14  -- X offset (x4 - x1)
+	dy14  -- Y offset (y4 - y1)
+.fi
+.ke
+
+These parameters perform the following functions:
+
+.ls 4
+.ls 16 ptable1
+The name of the first input photometry table. This should be a standard
+DAOPHOT output table or one whose column names have been modified to agree 
+with the DAOPHOT standard.
+.le
+.ls ptable2
+The name of the second input photometry table.
+.le
+.ls ptable3
+The name of the third input photometry table.
+.le
+.ls ptable4
+The name of the fourth input photometry table.
+.le
+.ls matchrad
+The matching radius for determining whether two objects should be identified
+with the same object and potentially included in the output table.
+.le
+.ls nmatch
+The minumum number of matches among the input photometry files for an object 
+to be included in the output Table. If there were four input files and
+\fInmatch\fR was set to two then an object would be included in the output
+if it was matched in files 1/2, 1/3, 1/4, 2/3, 2/4 or 3/4. If \fInmatch\fR
+was three then the object would have to be identified in files 1/2/3, 
+2/3/4, 1/2/4 or 1/3/4
+.le
+.ls gmfile12
+The name of the \fIGEOMAP\fR database containing the record which specifies 
+the transformation between photometry list 2 and photometry list 2 in the 
+sense of mapping objects in list #2 into the coordinate frame of the
+list #1
+.le
+.ls gmrec12
+The name of \fIGEOMAP\fR database record within \fIgmfile12\fR which
+describes the transformation from coordinate system #2 to system #1
+.le
+.ls gmfile13
+The name of the \fIGEOMAP\fR database containing the record which specifies 
+the transformation between photometry list 3 and photometry list 3 in the 
+sense of mapping objects in list #3 into the coordinate frame of the
+list #1
+.le
+.ls gmrec13
+The name of \fIGEOMAP\fR database record within \fIgmfile13\fR which
+describes the transformation from coordinate system #3 to system #1
+.le
+.ls gmfile14
+The name of the \fIGEOMAP\fR database containing the record which specifies 
+the transformation between photometry list 4 and photometry list 4 in the 
+sense of mapping objects in list #4 into the coordinate frame of the
+list #1
+.le
+.ls gmrec14
+The name of \fIGEOMAP\fR database record within \fIgmfile14\fR which
+describes the transformation from coordinate system #4 to system #1
+.le
+.ls dx12
+The X offset between coordinate system #2 and coordinate system #1
+in the sense of (x2 - x1).
+.le
+.ls dy12
+The Y offset between coordinate system #2 and coordinate system #1
+in the sense of (y2 - y1).
+.le
+.ls dx13
+The X offset between coordinate system #3 and coordinate system #1
+in the sense of (x3 - x1).
+.le
+.ls dy13
+The Y offset between coordinate system #3 and coordinate system #1
+in the sense of (y3 - y1).
+.le
+.ls dx14
+The X offset between coordinate system #4 and coordinate system #1
+in the sense of (x4 - x1).
+.le
+.ls dy14
+The Y offset between coordinate system #4 and coordinate system #1
+in the sense of (y4 - y1).
+.le
+.le
+
+If the parameters specifying the \fIGEOMAP\fR database file name for
+a particular transformation is empty then the corresponding parameters
+describing the transformation in terms of a simple shift are queried.
+
+.sh
+3.3.2
+The Output from MERGE
+
+\fIMERGE\fR will produce an STSDAS Table as output with the table
+containing pointers to records in the input Tables which identify the
+objects which are positionally coincident. The output Table will contain
+columns with the names \fIpoint0\fR, \fIpoint1\fR, \fIpoint2\fR and
+\fIpoint3\fR. If an object is identified in a particular input photometry
+list and also meets the \fInmatch\fR criterion then the entry in the 
+output Table will contain the row number in the corrsponding input Table.
+For those objects which are included in the output Table but which are not
+identified in a particular input Table the corrsponding entry will be
+INDEF.
+
+.ks
+.nf
+Sample Output Format (ASCII representation)
+
+ Point0		Point1		Point2		Point3
+
+ 1		3		INDEF		2
+ 3		2		2		4
+ 4		5		4		INDEF
+ INDEF		8		7		6
+
+ .fi
+ .ke
+
+ In the above sample the first matched object corrsponds to rows 1, 3 and
+ 2 in input Tables 0, 1 and 3 respectively. This object was not matched
+ in input Table 0. 
+
+The header of the Table output by MERGE shall contain the necessary information
+for tracking the original data files, the data and time the merge was done etc.
+The MSELECT task should check that the original photometry files have not been
+modified since MERGE was run to ensure data integrity.
+
+.sh
+3.4 MSELECT
+
+This task is used to select fields from the photometry Tables which
+were used as input to the \fIMERGE\fR task. The output from \fIMERGE\fR
+is a set of pointers to the appropriate records in the input tables.
+Using \fIMSELECT\fR on an output file from \fIMERGE\fR will produce an
+output file which will contain the specified fields for each of the
+objects which have been matched. If an object has not been identified
+in a particular Table then the values for each output field are set to
+INDEF.
+
+.sh
+3.4.1 MSELECT Parameters
+
+MERGE will have parameters wich will control the input and functioning
+of the task.
+
+.ks
+.nf
+Positional Parameters:
+
+	input		filename	""
+	fields		string		""
+	output		string		""
+.fi
+.ke
+
+.ks
+.nf
+Hidden Parameters:
+
+	tables		string		""
+.fi
+.ke
+
+These parameters perform the following functions:
+
+.ls 4
+.ls 16 input
+This specifies the input Table which must be an output Table from the
+\fIMERGE\fR task. \fIMSELECT\fR will get the names of the actual
+photometry Tables from the header of the input merge table.
+.le
+.ls fields
+A list of fields to extract from the input photometry tables. 
+.le
+.ls output
+The name of the output table. This table will contain entries for
+each of the selected fields of each photometry table. The values for
+each field in the output table will be the values of the selected fields
+for each of the input photometry tables. For those entries which were not 
+nmatched the corresponding entries will be INDEF.
+.le
+.ls tables
+This parameter is used to select output for only a subset of the input
+photometry tables. 
+.le
+
+.endhelp