imwcs(1)						      General Commands Manual							  imwcs(1)

Name
       imwcs - Set WCS in FITS and IRAF image files

Synopsis
       imwcs [options] FITS or IRAF filename

Description
       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 writ-
       ten at the University of Iowa, but has been adapted and amplified by Doug Mink at the Smithsonian Astrophysical Observatory.

       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, the USNO A 1.0, SA 1.0, or UJ Catalog, or a user-supplied, tab-
       delimited Starbase catalog may be used.

Options
       -a <angle>
	      Initial rotation angle in degrees (default 0)

       -b <RA> <Dec>
	      Initial center in B1950 (FK4) RA and Dec (default=RA,DEC from file)

       -c <catalog name>
	      Reference catalog (gsc(=HST GSC), ua2(=USNO-A2.0), TMC(=2MASS Point Source Catalog), gsc2(=GSC  II),  ub1(=USNO-B1.0),  local  file,
	      etc.)

       -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.

       -e     Erase image WCS keywords, getting initial WCS from command line

       -f     Write FITS output no matter what input

       -g <class>
	      Guide Star Catalog class (-1=all,0,3) (default -1)

       -h <number>
	      Change the maximum number of reference stars to match from 25 to

       -i <counts>
	      Minimum peak value for star in image.  If negative, use -<counts> standard deviations as minimum.

       -j <RA> <Dec>
	      Initial center in J2000 (FK5) RA and Dec (default=RA,DEC from file)

       -k <magnum>
	      Use this magnitude to sort brightest catalog stars.

       -l     Reflect left<->right before rotating and fitting

       -m [<bright magnitude>] <faint magnitude>
	      Limiting catalog magnitude(s) (default none, bright -2 if only faint is given)

       -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  refer-
	      ence pixel, and 8=Dec reference pixel.

       -o <filename>
	      Write output to this file; may be the same as input file.  This option automatically sets the -w option to write the file.

       -p <scale>
	      Initial plate scale in arcsec per pixel (default 0)

       -q <option list>
	      <i>terate,  <r>ecenter,  <s>igma	clip,  <p>olynomial,  <t>olerance  reduce (half for each iteration).  A number following an option
	      repeats the option that many times.

       -r <angle>
	      Rotation angle in degrees before fitting (0, 90, 180, 270) (default 0)

       -s <frac>
	      Use this fraction extra stars (default 1.0)

       -t <num>
	      Offset tolerance in pixels (default 20)

       -u <file>
	      File of X Y RA Dec assignments for initial WCS

       -v     Verbose listing of processing intermediate results

       -w     Write WCS to a new file (default is read-only) -x X and Y coordinates of reference pixel (default is image center) -y multiply image
	      dimensions  by  this  for search (default is 1) -z Use AIPS classic projections instead of WCSLIB; use CD matrix or CDELT instead of
	      polynomial solution.

Web Page
       http://tdc-www.harvard.edu/software/wcstools/imwcs/

Author
       Doug Mink, SAO (dmink@cfa.harvard.edu)

30 January 2003 						     WCSTools								  imwcs(1)