[fitswcs] RADECSYS keyword values

[Mark Calabretta]

On Mon 1998/11/09 15:55:17 CDT, Arnold Rots wrote
in a message to: fitswcs at fits.cv.nrao.edu
and copied to: arots at head-cfa.harvard.edu (Arnold H. Rots)

>>From these frames, a reference system, ICRS, was derived that is meant
>to be used as the successor of FK5, to express the coordinates of any
>object in an inertial frame.  Though one might be justified in
>labeling the coordinates of sources that were used in the definition
>of the ICRF with RADECSYS='ICRF', it would seem to me that 'ICRS' is
>the proper designation for everything else.

You could say something similar for the other RADECSYS keywords, FK4 and FK5.
These systems are often referred to as B1950/FK4 and J2000/FK5 where even
here the system designations are just a shorthand.  The issue really is to
set it to something now so that we don't end up having to recognize both
"ICRF" and "ICRS" and I think "ICRF" fits better with what's gone before.

Cheers, Mark