NRAO has a C library of World Coordinate System conversion routines.
It is not quite ready to be released; when it is available, I propose, as
a first step, to incorporate it into saoimage to provide sky position
feedback in parallel to the image coordinate feedback already provided.
The resulting modified program will be made available as soon as possible.
Client-side coordinate grids can be added later.
Through the grapevine I have heard that Mike van Hilst, author of saoimage
but no longer at SAO, has begun updating the program for release by the
Free Software Foundation as a public domain image display program. I
will be in touch with him about including WCS in his new program.
-Doug Mink (mink@cfa.harvard.edu)
Telescope Data Center
Harvard-Smithsonian Center for Astrophysics
Cambridge, Massachusetts