- NAME
ADXY
- PURPOSE
Use a FITS header to convert astronomical to pixel coordinates
- EXPLANATION
Use an image header to compute X and Y positions, given the
RA and Dec (or longitude, latitude) in decimal degrees.
- CALLING SEQUENCE
ADXY, HDR ;Prompt for Ra and DEC
ADXY, hdr, a, d, x, y, [ /PRINT, ALT= ]
- INPUTS
HDR - FITS Image header containing astrometry parameters
- OPTIONAL INPUTS
A - Right ascension in decimal DEGREES, scalar or vector
D - Declination in decimal DEGREES, scalar or vector
If A and D are not supplied, user will be prompted to supply
them in either decimal degrees or HR,MIN,SEC,DEG,MN,SC format.
- OPTIONAL OUTPUT
X - row position in pixels, same number of elements as A and D
Y - column position in pixels
X and Y will be in standard IDL convention (first pixel is 0) and not
the FITS convention (first pixel is 1). As in FITS an integral
value corresponds to the center of a pixel.
- OPTIONAL KEYWORD INPUT
/PRINT - If this keyword is set and non-zero, then results are displayed
at the terminal.
ALT - single character 'A' through 'Z' or ' ' specifying an alternate
astrometry system present in the FITS header. The default is
to use the primary astrometry or ALT = ' '. If /ALT is set,
then this is equivalent to ALT = 'A'. See Section 3.3 of
Greisen & Calabretta (2002, A&A, 395, 1061) for information about
alternate astrometry keywords.
- OPERATIONAL NOTES
If less than 5 parameters are supplied, or if the /PRINT keyword is
set, then the X and Y positions are displayed at the terminal.
If the procedure is to be used repeatedly with the same header,
then it would be faster to use AD2XY.
- PROCEDURES CALLED
AD2XY, ADSTRING(), EXTAST, GETOPT(), TEN()
- REVISION HISTORY
W. Landsman HSTX January, 1988
Use astrometry structure W. Landsman January, 1994
Changed default ADSTRING format W. Landsman September, 1995
Check if latitude/longitude reversed in CTYPE keyword W. L. Feb. 2004
Added ALT keyword W. Landsman September 2004
Work for non-spherical coordinate transformation W. Landsman May 2005
More informative error message if astrometry missing W.L. Feb 2008
Cosmetic updates W.L. July 2011
Use version 2 astrometry structure J. P. Leahy July 2013