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+.help ccsetwcs Jun99 images.imcoords
+.ih
+NAME
+ccsetwcs -- create an image wcs from a plate solution 
+.ih
+USAGE
+ccsetwcs image database solutions
+.ih
+PARAMETERS
+.ls images
+The input images for which the wcs is to be created.
+.le
+.ls database
+The text database file written by the ccmap task containing the
+plate solutions. If database is undefined ccsetwcs computes
+the image wcs using the xref, yref, xmag, ymag, xrotation, yrotation,
+lngref, latref, lngrefunits, latrefunits, and projection parameters.
+.le
+.ls solutions
+The list of plate solutions. The number of plate solutions must be one
+or equal to the number of input images.  Solutions is either a user name
+supplied to the ccmap task, or the
+name of the ccmap task input image for which the plate solution is valid,
+or the name of the coordinate file that the ccmap task used to compute the
+plate solution. The quantities stored in transform always supersede the
+values of the xref, yref, xmag, ymag, xrotation, yrotation, lngref, latref,
+lnrefunits, latrefunits, and projection parameters.
+.le
+.ls xref = INDEF, yref = INDEF
+The x and y pixel coordinates of the sky projection reference point.
+If database is undefined then xref and yref default to the center of the
+image in pixel coordinates, otherwise these parameters are ignored.
+.le
+.ls xmag = INDEF, ymag = INDEF
+The x and y scale factors in arcseconds per pixel. If database is undefined
+xmag and ymag default to 1.0 and 1.0 arcsec / pixel, otherwise these parameters
+are ignored.
+.le
+.ls xrotation = INDEF, yrotation = INDEF
+The x and y rotation angles in degrees measured counter-clockwise with
+respect to the x and y axes. Xrotation and yrotation are interpreted as the
+rotation of the coordinates with respect to the x and y axes and default 0.0
+and 0.0 degrees. For example xrotation and yrotation values of 30.0 and 30.0
+will rotate a point 30 degrees counter-clockwise with respect to the x and y
+axes. To flip the x axis coordinates in this case either set the angles to
+210.0 and 30.0 degrees or leave the angles set to 30.0 and 30.0 and set the
+xmag parameter to a negative value. To set east to the up, down, left, and
+right directions, set xrotation to 90, 270, 180, and 0 respectively. To set
+north to the up, down, left, and right directions, set yrotation to  0, 180,
+90, and 270 degrees respectively. Any global rotation must be added to both the
+xrotation and yrotation values.
+.le
+.ls lngref = INDEF, latref = INDEF
+The celestial coordinates of the sky projection reference point, e.g.
+the ra and dec of the reference point for equatorial systems. If database is
+undefined lngref and latref default to 0.0 and 0.0, otherwise these parameters
+are ignored.
+.le
+.ls lngunits = "", latunits = ""
+The units of the lngref and latref parameters.
+The options are "hours", "degrees", "radians" for the ra / longitude
+coordinates, and "degrees" and "radians" for the dec / latitude coordinates.
+If database is undefined then lngunits and latunits default to the preferred
+units for the celestial coordinate system defined by the \fIcoosystem\fR
+parameter, otherwise these parameters are ignored.
+.le
+.ls transpose = no
+Transpose the newly created image wcs ?
+.le
+.ls projection = "tan"
+The sky projection geometry. The most commonly used projections in
+astronomy are "tan", "arc", "sin", and "lin". Other supported projections
+are "ait", "car", "csc", "gls", "mer", "mol", "par", "pco", "qsc", "stg",
+"tsc", and "zea".
+.le
+.ls coosystem = "j2000"
+The celestial coordinate system. The systems of most interest to users
+are "icrs", "j2000" and "b1950" which stand for the ICRS J2000.0, FK5 J2000.0,
+and FK4 B1950.0 celestial coordinate systems respectively. The full set of
+options are listed below. The celestial coordinate system sets the preferred
+units for the lngref and latref parameters and the correct values of the image
+wcs header keywords CTYPE, RADECSYS, EQUINOX, and MJD-WCS if the image header
+wcs is updated.  If database is undefined the coosystem parameter is used,
+otherwise this parameter is ignored.
+
+.ls equinox [epoch]
+The equatorial mean place post-IAU 1976 (FK5) system if equinox is a
+Julian epoch, e.g. J2000.0 or 2000.0, or the equatorial mean place
+pre-IAU 1976 system (FK4) if equinox is a Besselian epoch, e.g. B1950.0
+or 1950.0. Julian equinoxes are prefixed by a J or j, Besselian equinoxes
+by a B or b. Equinoxes without the J / j or B / b prefix are treated as
+Besselian epochs if they are < 1984.0, Julian epochs if they are >= 1984.0.
+Epoch is the epoch of the observation and may be a Julian
+epoch, a Besselian epoch, or a Julian date. Julian epochs
+are prefixed by a J or j, Besselian epochs by a B or b.
+Epochs without the J / j or B / b prefix default to the epoch type of
+equinox if the epoch value <= 3000.0, otherwise epoch is interpreted as
+a Julian date.  If undefined epoch defaults to equinox.
+.le
+.ls icrs [equinox] [epoch]
+The International Celestial Reference System where equinox is
+a Julian or Besselian epoch e.g. J2000.0  or B1980.0.
+Equinoxes without the J / j or B / b prefix are treated as Julian epochs.
+The default value of equinox is J2000.0.
+Epoch is a Besselian epoch, a Julian epoch, or a Julian date.
+Julian epochs are prefixed by a J or j, Besselian epochs by a B or b.
+Epochs without the J / j or B / b prefix default to Julian epochs
+if the epoch value <= 3000.0, otherwise epoch is interpreted as
+a Julian date.  If undefined epoch defaults to equinox.
+.le
+.ls fk5 [equinox] [epoch] 
+The equatorial mean place post-IAU 1976 (FK5) system where equinox is
+a Julian or Besselian epoch e.g. J2000.0  or B1980.0.
+Equinoxes without the J / j or B / b prefix are treated as Julian epochs.
+The default value of equinox is J2000.0.
+Epoch is a Besselian epoch, a Julian epoch, or a Julian date.
+Julian epochs are prefixed by a J or j, Besselian epochs by a B or b.
+Epochs without the J / j or B / b prefix default to Julian epochs
+if the epoch value <= 3000.0, otherwise epoch is interpreted as
+a Julian date.  If undefined epoch defaults to equinox.
+.le
+.ls fk4 [equinox] [epoch]
+The equatorial mean place pre-IAU 1976 (FK4) system where equinox is a
+Besselian or Julian epoch e.g. B1950.0  or J2000.0,
+and epoch is the Besselian epoch, the Julian epoch, or the Julian date of the
+observation.
+Equinoxes without the J / j or B / b prefix are treated
+as Besselian epochs. The default value of equinox is B1950.0. Epoch
+is a Besselian epoch, a Julian epoch, or a Julian date.
+Julian epochs are prefixed by a J or j, Besselian epochs by a B or b.
+Epochs without the J / j or B / b prefix default to Besselian epochs
+if the epoch value <= 3000.0, otherwise epoch is interpreted as
+a Julian date.  If undefined epoch defaults to equinox.
+.le
+.ls noefk4 [equinox] [epoch]
+The equatorial mean place pre-IAU 1976 (FK4) system but without the E-terms
+where equinox is a Besselian or Julian epoch e.g. B1950.0 or J2000.0,
+and epoch is the Besselian epoch, the Julian epoch, or the Julian date of the
+observation.
+Equinoxes without the J / j or B / b prefix are treated
+as Besselian epochs. The default value of equinox is B1950.0.
+Epoch is a Besselian epoch, a Julian epoch, or a Julian date.
+Julian epochs are prefixed by a J or j, Besselian epochs by a B or b.
+Epochs without the J / j or B / b prefix default to Besselian epochs
+if the epoch value <= 3000.0, otherwise epoch is interpreted as
+a Julian day.  If undefined epoch defaults to equinox.
+.le
+.ls apparent epoch 
+The equatorial geocentric apparent place post-IAU 1976 system where
+epoch is the epoch of observation.
+Epoch is a Besselian epoch, a Julian epoch or a Julian date.
+Julian epochs are prefixed by a J or j, Besselian epochs by a B or b.
+Epochs without the J / j or B / b prefix default to Besselian
+epochs if the epoch value < 1984.0, Julian epochs
+if the epoch value <= 3000.0, otherwise epoch is interpreted as
+a Julian date.
+.le
+.ls ecliptic epoch
+The ecliptic coordinate system where epoch is the epoch of observation.
+Epoch is a Besselian epoch, a Julian epoch, or a Julian date.
+Julian epochs are prefixed by a J or j, Besselian epochs by a B or b.
+Epochs without the J / j or B / b prefix default to Besselian epochs
+if the epoch values < 1984.0, Julian epochs
+if the epoch value <= 3000.0, otherwise epoch is interpreted as
+a Julian day.
+.le
+.ls galactic [epoch]
+The IAU 1958 galactic coordinate system.
+Epoch is a Besselian epoch, a Julian epoch or a Julian date.
+Julian epochs are prefixed by a J or j, Besselian epochs by a B or b.
+Epochs without the J / j or B / b prefix default to Besselian
+epochs if the epoch value < 1984.0, Julian epochs
+if the epoch value <= 3000.0, otherwise epoch is interpreted as
+a Julian date. The default value of epoch is B1950.0.
+.le
+.ls supergalactic [epoch]
+The deVaucouleurs supergalactic coordinate system.
+Epoch is a Besselian epoch, a Julian epoch or a Julian date.
+Julian epochs are prefixed by a J or j, Besselian epochs by a B or b.
+Epochs without the J / j or B / b prefix default to Besselian
+epochs if the epoch value < 1984.0, Julian epochs
+if the epoch value <= 3000.0, otherwise epoch is interpreted as
+a Julian date. The default value of epoch is B1950.0.
+.le
+
+In all the above cases fields in [] are optional with the defaults as
+described. The epoch field for icrs, fk5, galactic, and supergalactic
+coordinate systems is required only if the input coordinates are in the
+equatorial fk4, noefk4, fk5, or icrs systems and proper motions are defined.
+.le
+.ls update = yes
+Update the world coordinate system in the input image headers ?
+The numerical quantities represented by the keywords CRPIX,
+CRVAL, and CD are computed from the linear portion of the plate solution.
+The values of the keywords CTYPE, RADECSYS, EQUINOX, and MJD-WCS
+are set by the \fIprojection\fR and \fIcoosystem\fR parameters if database
+is undefined, otherwise projection and coosystem are read from the plate
+solution. As there is currently no standard mechanism for storing the higher
+order plate solution terms if any in the image header wcs, these terms are
+ignored. Any existing image wcs represented by the above keywords is
+overwritten during the update.
+.le
+.ls pixsystem = "logical"
+The pixel coordinate system. The options are:
+.ls logical
+The logical pixel coordinate system is the coordinate system of the image
+pixels on disk. Since most users measure the pixel coordinates of objects
+in this system, "logical" is the system of choice for most applications.
+.le
+.ls physical
+The physical coordinate system is the pixel coordinate system of the
+parent image. This option is useful for users working on images that are
+pieces of a larger mosaic.
+.le
+
+The pixsystem parameter is only used if no database solution is specified.
+Otherwise pixsystem is read from the database file.
+.le
+.ls verbose = yes
+Print detailed messages about the progress of the task on the standard output ?
+.le
+
+.ih
+DESCRIPTION
+
+CCSETWCS creates an image world coordinate system from the plate solution
+computed by the CCMAP task or supplied by the user, and writes it to the
+headers of the input images \fIimages\fR if the \fIupdate\fR parameter is yes.
+
+The plate solution can either be read from record \fIsolutions\fR in the
+database file \fIdatabase\fR written by CCMAP, or specified by the user
+via the \fIxref\fR, \fIyref\fR, \fIxmag\fR, \fIymag\fR, \fIxrotation\fR,
+\fIyrotation\fR, \fIlngref\fR, \fIlatref\fR, \fIlngunits\fR, \fIlatunits\fR,
+\fItranspose\fR, \fIprojection\fR, \fIcoosystem\fR and \fIpixsystem\fR
+parameters.
+
+The plate solution computed by CCMAP has the following form where x and y
+are the image pixel coordinates and xi and eta are the corresponding standard
+coordinates in arcseconds per pixel. The standard coordinates are computed
+by applying the appropriate sky projection to the celestial coordinates.
+
+
+.nf
+	 xi = f (x, y)
+	eta = g (x, y)
+.fi
+
+The functions f and g are either power series, Legendre, or Chebyshev
+polynomials whose order and region of validity were set by the user when
+CCMAP was run. The computed plate solution is somewhat arbitrary and does
+not correspond to any physically meaningful model. However the linear
+component of the plate solution can be given the simple geometrical
+interpretation shown below.
+
+.nf
+	  xi = a + b * x + c * y
+	 eta = d + e * x + f * y
+	   b = xmag * cos (xrotation)
+	   c = ymag * sin (yrotation)
+	   e = -xmag * sin (xrotation)
+	   f = ymag * cos (yrotation)
+	   a = xi0 - b * xref - c * yref = xshift
+	   d = eta0 - e * xref - f * yref = yshift
+	   xi0 = 0.0
+	   eta0 = 0.0
+.fi
+
+xref, yref, xi0, and eta0 are the origins of the pixel and standard
+coordinate systems respectively. xmag and ymag are the x and y scale factors
+in " / pixel and xrotation and yrotation are the rotation angles measured
+counter-clockwise of the x and y axes.
+
+If the CCMAP database is undefined then CCSETWCS computes a linear plate
+solution using the parameters \fIxref\fR, \fIyref\fR, \fIxmag\fR,
+\fIymag\fR, \fIxrotation\fR, \fIyrotation\fR, \fIlngref\fR, \fIlatref\fR,
+\fIlngunits\fR, \fIlatunits\fR, \fItranspose\fR,  and
+\fIprojection\fR as shown below. Note that in this case
+xrotation and yrotation are interpreted as the rotation of the coordinates
+themselves not the coordinate axes. 
+
+.nf
+	  xi = a + b * x + c * y
+	 eta = d + e * x + f * y
+	   b = xmag * cos (xrotation)
+	   c = -ymag * sin (yrotation)
+	   e = xmag * sin (xrotation)
+	   f = ymag * cos (yrotation)
+	   a = xi0 - b * xref - c * yref = xshift
+	   d = eta0 - e * xref - f * yref = yshift
+	   xi0 = 0.0
+	   eta0 = 0.0
+.fi
+
+The \fItranspose\fR parameter can be used to transpose the newly created
+image wcs.
+
+If the \fIupdate\fR switch is "yes" and an input image is specified,
+a new image wcs is derived from the linear component of the computed plate
+solution and written to the image header. The numerical components of
+the new image wcs are written to the standards FITS keywords, CRPIX, CRVAL,
+and CD, with the actual values depending on the pixel coordinate system
+\fIpixsystem\fR read from the database or set by the user. The FITS keywords
+which define the image celestial coordinate system CTYPE, RADECSYS, EQUINOX,
+and MJD-WCS are set by the \fIcoosystem\fR and \fIprojection\fR parameters.
+
+The first four characters of the values of the ra / longitude and dec / latitude
+axis CTYPE keywords specify the celestial coordinate system. They are set to
+RA-- / DEC- for equatorial coordinate systems, ELON / ELAT for the ecliptic
+coordinate system, GLON / GLAT for the galactic coordinate system, and
+SLON / SLAT for the supergalactic coordinate system.
+
+The second four characters of the values of the ra / longitude and dec /
+latitude axis CTYPE keywords specify the sky projection geometry.
+The second four characters of the values of the ra / longitude and dec /
+latitude axis CTYPE keywords specify the sky projection geometry. IRAF
+currently supports the TAN, SIN, ARC, AIT, CAR, CSC, GLS, MER, MOL, PAR, PCO,
+QSC, STG, TSC, and ZEA standard projections, in which case the second 4
+characters of CTYPE are set to  -TAN, -ARC, -SIN, etc.
+
+If the input celestial coordinate system is equatorial, the value of the
+RADECSYS keyword specifies the fundamental equatorial system, EQUINOX
+specifies the epoch of the mean place, and MJD-WCS specifies the epoch
+for which the mean place is correct. The permitted values of
+RADECSYS are FK4, FK4-NO-E, FK5, ICRS, and GAPPT. EQUINOX is entered in years
+and interpreted as a Besselian epoch for the FK4 system, a Julian epoch
+for the FK5 and ICRS system. The epoch of the wcs MJD-WCS is entered as
+a modified Julian date. Only those keywords necessary to defined the
+new wcs are written. Any existing keywords which are not required to
+define the wcs or are redundant are removed, with the exception of
+DATE-OBS and EPOCH, which are left unchanged for obvious (DATE-OBS) and
+historical (use of EPOCH keyword at NOAO) reasons.
+
+If \fIverbose\fR is "yes", various pieces of useful information are
+printed to the terminal as the task proceeds.
+
+.ih
+REFERENCES
+
+Additional information on the IRAF world coordinate systems can be found in
+the help pages for the WCSEDIT and WCRESET tasks.
+Detailed documentation for the IRAF world coordinate system interface MWCS
+can be found in the file "iraf$sys/mwcs/MWCS.hlp". This file can be
+formatted and printed with the command "help iraf$sys/mwcs/MWCS.hlp fi+ |
+lprint".
+
+Details of the FITS header world coordinate system interface can
+be found in the draft paper "World Coordinate Systems Representations Within the
+FITS Format" by Hanisch and Wells, available from the iraf anonymous ftp
+archive and the draft paper which supersedes it "Representations of Celestial
+Coordinates in FITS" by Greisen and Calabretta available from the NRAO
+anonymous ftp archives.
+
+The spherical astronomy routines employed here are derived from the Starlink
+SLALIB library provided courtesy of Patrick Wallace. These routines
+are very well documented internally with extensive references provided
+where appropriate. Interested users are encouraged to examine the routines
+for this information. Type "help slalib" to get a listing of the SLALIB
+routines, "help slalib opt=sys" to get a concise summary of the library,
+and "help <routine>" to get a description of each routine's calling sequence,
+required input and output, etc. An overview of the library can be found in the
+paper "SLALIB - A Library of Subprograms", Starlink User Note 67.7
+by P.T. Wallace, available from the Starlink archives.
+
+
+
+.ih
+EXAMPLES
+
+1. Compute the plate solution for an image with the ccmap task and then
+use the ccsetwcs task to create the image wcs. Check the results with the
+imheader and skyctran tasks.
+
+.nf
+cl> type coords
+13:29:47.297  47:13:37.52  327.50  410.38
+13:29:37.406  47:09:09.18  465.50   62.10
+13:29:38.700  47:13:36.23  442.01  409.65
+13:29:55.424  47:10:05.15  224.35  131.20
+13:30:01.816  47:12:58.79  134.37  356.33
+
+
+cl> ccmap coords coords.db image=pix xcol=3 ycol=4 lngcol=1 latcol=2 \
+inter-
+Coords File: coords  Image: pix
+    Database: coords.db  Record: pix
+Refsystem: j2000  Coordinates: equatorial FK5
+    Equinox: J2000.000 Epoch: J2000.00000000 MJD: 51544.50000
+Insystem: j2000  Coordinates: equatorial FK5
+    Equinox: J2000.000 Epoch: J2000.00000000 MJD: 51544.50000
+Coordinate mapping status
+    Ra/Dec or Long/Lat fit rms: 0.229  0.241   (arcsec  arcsec)
+Coordinate mapping parameters
+    Sky projection geometry: tan
+    Reference point: 13:29:48.129  47:11:53.37  (hours  degrees)
+    Reference point: 318.735  273.900  (pixels  pixels)
+    X and Y scale: 0.764  0.767  (arcsec/pixel  arcsec/pixel)
+    X and Y axis rotation: 179.110  358.958  (degrees  degrees)
+Wcs mapping status
+    Ra/Dec or Long/Lat wcs rms: 0.229  0.241   (arcsec  arcsec)
+
+cl> type coords.db
+# Mon 15:10:37 13-May-96
+begin   coords
+        xrefmean        318.7460000000001
+        yrefmean        273.9320000000001
+        lngmean         13.49670238888889
+        latmean         47.19815944444444
+        coosystem       j2000
+        projection      tan
+        lngref          13.49670238888889
+        latref          47.19815944444444
+        lngunits        hours
+        latunits        degrees
+        xpixref         318.7352667484295
+        ypixref         273.9002619912411
+        geometry        general
+        function        polynomial
+        xishift         247.3577084680361
+        etashift        -206.1795977453246
+        xmag            0.7641733802338992
+        ymag            0.7666917500560622
+        xrotation       179.1101291109185
+        yrotation       358.9582148846163
+        wcsxirms        0.2288984454992771
+        wcsetarms       0.2411034140453112
+        xirms           0.2288984454992771
+        etarms          0.2411034140453112
+        surface1        11
+                        3.      3.
+                        2.      2.
+                        2.      2.
+                        0.      0.
+                        134.3700000000001       134.3700000000001
+                        465.5000000000002       465.5000000000002
+                        62.1    62.1
+                        410.3800000000001       410.3800000000001
+                        247.3577084680361       -206.1795977453246
+                        -0.7640812161068504     -0.011868034832272
+                        -0.01393966623835092    0.7665650170136847
+        surface2        0
+
+
+
+cl> imheader pix l+
+...
+DATE-OBS= '05/04/87'            /  DATE DD/MM/YY
+RA      = '13:29:24.00'         /  RIGHT ASCENSION
+DEC     = '47:15:34.00'         /  DECLINATION
+EPOCH   =              1987.26  /  EPOCH OF RA AND DEC
+...
+
+
+cl> ccsetwcs pix coords.db pix 
+Image: pix  Database: coords.db  Record: pix
+Coordinate mapping parameters
+    Sky projection geometry: tan
+    Reference point: 13:29:48.129  47:11:53.37  (hours   degrees)
+    Ra/Dec logical image axes: 1  2
+    Reference point: 318.735  273.900  (pixels  pixels)
+    X and Y scale: 0.764  0.767  (arcsec/pixel  arcsec/pixel)
+    X and Y coordinate rotation: 179.110  358.958  (degrees  degrees)
+Updating image header wcs
+
+cl> imheader pix l+
+...
+DATE-OBS= '05/04/87'            /  DATE DD/MM/YY
+RA      = '13:29:24.00'         /  RIGHT ASCENSION
+DEC     = '47:15:34.00'         /  DECLINATION
+EPOCH   =              1987.26  /  EPOCH OF RA AND DEC
+...
+RADECSYS= 'FK5     '
+EQUINOX =                2000.
+MJD-WCS =              51544.5
+WCSDIM  =                    2
+CTYPE1  = 'RA---TAN'
+CTYPE2  = 'DEC--TAN'
+CRVAL1  =     202.450535833334
+CRVAL2  =     47.1981594444445
+CRPIX1  =     318.735266748429
+CRPIX2  =     273.900261991241
+CD1_1   =  -2.1224478225190E-4
+CD1_2   =  -3.8721295106530E-6
+CD2_1   =  -3.2966763422978E-6
+CD2_2   =  2.12934726948246E-4
+LTM1_1  =                   1.
+LTM2_2  =                   1.
+WAT0_001= 'system=image'
+WAT1_001= 'wtype=tan axtype=ra'
+WAT2_001= 'wtype=tan axtype=dec'
+
+cl> skyctran coords STDOUT "pix log" "pix world" lngcol=3 latcol=4 trans+
+
+# Insystem: pix logical  Projection: TAN  Ra/Dec axes: 1/2
+#     Coordinates: equatorial FK5 Equinox: J2000.000
+#     Epoch: J2000.00000000 MJD: 51544.50000
+# Outsystem: pix world  Projection: TAN  Ra/Dec axes: 1/2
+#     Coordinates: equatorial FK5 Equinox: J2000.000
+#     Epoch: J2000.00000000 MJD: 51544.50000
+
+# Input file: incoords  Output file: STDOUT
+
+13:29:47.297  47:13:37.52 13:29:47.284 47:13:37.89
+13:29:37.406  47:09:09.18 13:29:37.425 47:09:09.24
+13:29:38.700  47:13:36.23 13:29:38.696 47:13:35.95
+13:29:55.424  47:10:05.15 13:29:55.396 47:10:05.09
+13:30:01.816  47:12:58.79 13:30:01.842 47:12:58.70
+.fi
+
+The skyctran task is used to test that the input image wcs is indeed correct.
+Columns 1 and 2 contain the original ra and dec values and columns 3 and 4
+contain the transformed values. The second imheader listing shows what the
+image wcs looks like.
+
+
+2. Repeat the previous example but enter the plate solution parameters by
+hand.
+
+.nf
+cl> ccsetwcs pix "" xref=318.735 yref=273.900 lngref=13:29:48.129 \
+latref=47:11:53.37 xmag=.764 ymag=.767 xrot=180.890 yrot=1.042
+Image: pix
+Coordinate mapping parameters
+    Sky projection geometry: tan
+    Reference point: 13:29:48.129  47:11:53.37  (hours   degrees)
+    Ra/Dec logical image axes: 1  2
+    Reference point: 318.735  273.900  (pixels  pixels)
+    X and Y scale: 0.764  0.767  (arcsec/pixel  arcsec/pixel)
+    X and Y coordinate rotation: 180.890  1.042  (degrees  degrees)
+Updating image header wcs
+
+
+cl> skyctran coords STDOUT "pix log" "pix world" lngcol=3 latcol=4 trans+
+
+# Insystem: pix logical  Projection: TAN  Ra/Dec axes: 1/2
+#     Coordinates: equatorial FK5 Equinox: J2000.000
+#     Epoch: J2000.00000000 MJD: 51544.50000
+# Outsystem: pix world  Projection: TAN  Ra/Dec axes: 1/2
+#     Coordinates: equatorial FK5 Equinox: J2000.000
+#     Epoch: J2000.00000000 MJD: 51544.50000
+
+# Input file: incoords  Output file: STDOUT
+
+13:29:47.297  47:13:37.52 13:29:47.285 47:13:37.93
+13:29:37.406  47:09:09.18 13:29:37.428 47:09:09.17
+13:29:38.700  47:13:36.23 13:29:38.698 47:13:35.99
+13:29:55.424  47:10:05.15 13:29:55.395 47:10:05.04
+13:30:01.816  47:12:58.79 13:30:01.839 47:12:58.72
+.fi
+
+Note that there are minor differences between the results of examples 1
+and 2 due to precision differences in the input. Note also the difference
+in the way the xrotation and yrotation angles are defined between examples
+1 and 2. In example 2 the rotations are defined as coordinate rotations,
+whereas in example one they are described as axis rotations.
+
+.ih
+BUGS
+
+.ih
+SEE ALSO
+ccmap, cctran, skyctran, imctran
+.endhelp