idlastro / FITS Astrometry and Calibration: GSSSADXY

[Source code]

NAME
GSSSADXY
PURPOSE
Converts RA and DEC (J2000) to (X,Y) for an STScI GuideStar image.   
EXPLANATION
The sky coordinates may be printed and/or returned in variables.
CALLING SEQUENCE
GSSSADXY, GSA, Ra,Dec, [ X, Y, /Print ] 
INPUT
GSA - the GSSS Astrometry structure created by GSSSEXTAST
RA  - the RA coordinate(s) in *degrees*, scalar or vector
DEC - the DEC coordinate(s) in *degrees*, scalar or vector
OPTIONAL KEYWORD INPUT
/PRINT - If this keyword is set and non-zero, then coordinates will be
        displayed at the terminal
OUTPUT
X - the corresponding X pixel coordinate(s), double precision
Y - the corresponding Y pixel coordinate(s), double precision
X and Y will be in IDL convention (first pixel 0,0)
EXAMPLE
Given a FITS header, hdr, from the STScI Guidestar Survey, determine
the X,Y coordinates of 3C 273 (RA = 12 29 6.7  +02 03 08)
IDL> GSSSEXTAST, hdr, gsa          ;Extract astrometry structure
IDL> GSSSADXY, gsa, ten(12,29,6.7)*15,ten(2,3,8),/print
NOTES
For most purpose users can simply use ADXY, which will call GSSSADXY
if it is passed a GSSS header.
PROCEDURES CALLED
ASTDISP - Print RA, Dec in standard format
HISTORY
10-JUL-90 Version 1 written by Eric W. Deutsch
        Derived from procedures written by Brian McLean
Vectorized code   W. Landsman        March, 1991
14-AUG-91 Fixed error which caused returned X and Y to be .5 pixels too
        large.  Now X,Y follows same protocol as ADXY.
June 1994 - Dropped PRFLAG parameter, added /PRINT  W. Landsman (HSTX)
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
Reduce memory requirements for large arrays D. Finkbeiner April 2004
Remove