Convert (X,Y) coordinates in a STScI Guide Star image to RA and Dec
The sky coordinates may be printed and/or returned in variables.
GSSSxyad, gsa, x, y, ra, dec, [ /PRINT ]
GSA - The GSSS Astrometry structure extracted from a FITS header
X - The X pixel coordinate(s) of the image, scalar or vector
Y - The Y pixel coordinate(s) of the image, scalar or vector
RA - The RA coordinate of the given pixel(s) in *degrees*
DEC - The DEC coordinate of the given pixel(s) in *degrees*
Both RA and Dec will be returned as double precision
Optional Keyword Input
/PRINT - If this keyword is set and non-zero, then coordinates will be
displayed at the terminal
Given a FITS header,hdr, from a GSSS image, print the astronomical
coordinates of (X,Y) = (200.23, 100.16) at the terminal
IDL> GSSSExtast, hdr, gsa ;Extract astrometry structure
IDL> GSSSxyad, gsa, 200.23, 100.16, /print
For most purpose users can simply use XYAD, which will call GSSSXYAD
if it is passed a GSSS header.
ASTDISP - print RA, Dec in a standard format
01-JUL-90 Version 1 written by Eric W. Deutsch
Vectorized Code W. Landsman March, 1991
14-AUG-91 Fixed error which caused returned RA and DEC to be off by
-.5 pixels in both X,Y. Now X,Y follows same protocol as ADXY.
20-AUG-91 Modified to use AstDisp procedure.
June 94 Added /PRINT keyword instead of PRFLAG W. Landsman June 94
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