idlastro / FITS Astrometry and Calibration: GSSSEXTAST

[Source code]

NAME
GSSSEXTAST
PURPOSE
Extract IDL astrometry structure from a ST Guide Star Survey FITS header
EXPLANATION
This procedure extracts the astrometry information from a ST Guide
Star Survey FITS header and places it in an IDL structure for 
subsequent use with GSSSxyad and GSSSadxy.
CALLING SEQUENCE
GSSSExtast, hdr, astr, noparams
INPUT
h - the GSSS FITS header
OUTPUT
astr  - Structure containing the GSSS Astrometry information
         .CTYPE  =  ['RA---GSS','DEC--GSS'] 
         .CRVAL = plate center Ra, Dec (from PLTRAH, PLTRAM etc.)
         .XLL,.YLL = offsets lower lefthand corner
         .AMDX, .AMDY = 12 transformation coefficients
         .XSZ,.YSZ = X and Y pixel size in microns
         .PLTSCL = plate scale in arc sec/mm
         .PPO3, .PPO6 - orientation coefficients
NOTES
Most users should use EXTAST rather than this procedure.   EXTAST will
call GSSSEXTAST if supplied with GSSS FITS header.
PROCEDURES CALLED
SXPAR() - Extract parameter values from a FITS header
HISTORY
01-JUL-90 Version 1 written by Eric W. Deutsch
Code derived from Software by Brian McLean
20-AUG-91 Modified to Double Precision Variables.  E. Deutsch
June 94 Change astrometry tags to better agree with EXTAST  W. Landsman
Converted to IDL V5.0   W. Landsman   September 1997
29-JUN-99 Added support for AMD[X,Y]1[2-3] for DSS images by E. Deutsch
Eliminate use of obsolete !ERR  W. Landsman    February 2000