[daip] AIPS

[Eric Greisen]

Anna Scaife writes:

 > i was wondering - is there a way of converting cartesian galactic 
 > projection (GLON-CAR / GLAT-CAR) to J2000 in aips? I'm trying to use CGPS 
 > data if that's relelvant at all.
 > 

The first requirement will be to get away from the "linear"
description.  If the reference value for declination is zero AIPS can
help you, otherwise I do not know for sure what needs to be done.  As
our WCS paper II points out the -CAR coordinates are not so simple as
they may appear - see page 1081 and 1112 for discussions.  Paper II is
available as a pdf from my web site
        http://www.aoc.nrao.edu/~egreisen
If you re-grid the image into a projective geometry (-SIN or -TAN),
the J2000 conversion is a simple rotation.

The AIPS task to look at is REGRD primarily althoughh OHGEO and HGEOM
may be appropriate.  The latter 2 do not know about galactic
coordinates however and so can go from galactic to galactic or
celestial to celestial.  There are verb CELGAL (switch between
celestial and galactic) and EPOSW (switch 1950 and J2000).

Not knowing more about your data (is -CAR used correctly?) I do not
know what more to say.

Eric Greisen