APASS update

[Arne Henden]

Stephen Levine has analyzed the astrometry, and has written a program
that takes the linear coefficient output file from my pipeline and
applies a 3rd order polynomial fit to the residuals. The result is
that the images now have less than 0.25arcsec mean errors across the
entire field, with many frames under 0.15arcsec.

We are now moving on to the photometric correction task. Matt is
matching SDSS gri data with three APASS fields to generate photometric
error maps to see what systematics remain. I expect that task to be
finished within a week or so.

Once we have the astrometric and photometric corrections applied, I
will re-release DR0 so that the datamining section can investigate
further. That should be in early April. In the meantime, APASS has
been continuing to extend its coverage, working on fields from +30 to
+60 declination.
Arne