Re: [TASS] photometric vs. non-photometric

["Arne A. Henden" <aah@NOFS.NAVY.MIL>]

At one point I understood the TASS database files, but
I now have forgotten everything.  I thought Chris set
it up with a 'seed' catalog so that all TASS objects were
matched against its coordinates.  An obvious seed catalog
would be GSC 1.2.  Then retain the seed coordinates for
future matching, but have two additional columns of TASS RA and DEC
for comparison.
  The real problem on seeding is getting the resolution
to match the TASS 14arcsec pixels.  This is especially true
in the Milky Way where there may be several stars within
15arcsec of the TASS coordinate; which one do you match it
with?
  I've got it easier with my personal database, since our
CCDs give subarcsec astrometry.  Matching is then just a
matter of selecting stars within an arcsec radius.  Even
there, when I get into crowded regions, I get mismatches
due to both close neighbors and the effect of bright
neighbors on the centroiding.  It takes a really smart person
to get catalog matching correct.
Arne