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.help imwcs Apr2004 WCSTools
imwcs -- Set WCS in FITS and IRAF image files
imwcs [options] FITS or IRAF filename
.I imwcs
(pronounced im-W-C-S) is a utility for setting the world coordinate system
(WCS) of a FITS or IRAF image. The WCS is the relationship between sky
coordinates and image pixels and can be described in a standard way in the
header of an image. The program was originally written at the University
of Iowa, but has been adapted and amplified by Doug Mink at the Smithsonian
Astrophysical Observatory. 
.I imwcs
currently works only on images where the rotation about the center is
known to within a few degrees It has been tested extensively only on
images with near-zero rotation. 
A plane-tangent projection (center right ascension and declination, plate
scale, and rotation angle) is fit based on matches between stars in the
image and stars in a reference catalog. The HST Guide Star Catalog, GSC II,
USNO B1.0, A2.0, SA2.0, or UCAC2 Catalog, 2MASS Point Source Catalog, or
a user-supplied, plain ASCII or tab-delimited Starbase catalog may be used. 
.ls -a <angle>
Initial rotation angle in degrees (default 0)
.ls -b <RA> <Dec>
Initial center in B1950 (FK4) RA and Dec (default=RA,DEC from file)
.ls -c <catalog name>
Reference catalog (gsc, uac, ujc, usac, or tab table file) (default=gsc)
.ls -d <catalog name>
Use this DAOFIND output catalog of X, Y, and magnitude instead of searching
for stars in the image.  The format is simply white-space-separated X, Y,
and magnitue on a line, with # at the beginning of comment lines.
.ls -f
Write FITS output no matter what input
.ls -g <class>
Guide Star Catalog class (-1=all,0,3) (default -1)
.ls -h <number>
Change the maximum number of reference stars to match from 25 to
.B <number>

.ls -i <counts>
Minimum peak value for star in image.  If negative, use -<counts> standard
deviations as minimum.
.ls -j <RA> <Dec>
Initial center in J2000 (FK5) RA and Dec (default=RA,DEC from file)
.ls -l
Reflect left<->right before rotating and fitting
.ls -m [<bright magnitude>] <faint magnitude>
Limiting catalog magnitude(s) (default none, bright -2 if only faint is given)
.ls -n <number>
Number of parameters to fit (1-8, or digit string). The default is 2 (RA+Dec)
if <3 stars are matched, 3 (RA+Dec+scale) if <5 stars are matched, or
4 (RA+Dec+scale+rot) if 5 or more stars are matched.  Alternatively this
may be a list of all of the parameters to fit, in the form nnnnnn..,
where 1=RA, 2=Dec, 3=RA scale, 4=Dec scale, 5=rotation angle, 6=Y axis
rotation (CD matrix), 7=RA reference pixel, and 8=Dec reference pixel.
.ls -o <filename>
Write output to this file; may be the same as input file.  This option
automatically sets the
.ls -w
option to write the file.
.ls -p <scale>
Initial plate scale in arcsec per pixel (default 0)
.ls -r <angle>
Rotation angle in degrees before fitting (0, 90, 180, 270) (default 0)
.ls -s <frac>
Use this fraction extra stars (default 1.0)
.ls -t <num>
Offset tolerance in pixels (default 20)
.ls -u <num>
USNO catalog single plate number to accept (default all)
.ls -v
Verbose listing of processing intermediate results
.ls -w
Write WCS to a new file (default is read-only)
.ls -x
X and Y coordinates of reference pixel (default is image center)
.ls -y
multiply image dimensions by this for search (default is 1)
.ls -z
Use AIPS classic projections instead of WCSLIB; use CD matrix or CDELT
instead of polynomial solution.
Doug Mink, SAO (

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