| I've made a catalog of object appropriate for astrometrically calibrating
other bands to the F22I.
The criteria are (in SExtractor terms):
MAG_APER < 22.5
MAG_AUTO > MAG_APER -1
FLAGS == 0
where MAG_APER is measured in a 3 arcsecond diameter aperture.
-
MAG_APER < 22.5 means things are reasonably bright.
-
MAG_AUTO > MAG_APER -1 gets rid of spurious sources
on fringes, internal reflections,satellite trails, saturated star spikes
and rings. This means hand-drawn masks aren't necessary. Obviously we don't
want large patches with no objects (as is the case with masks); the astrometry
in those regions would suffer. This condition also ensures (to some degree)
that objects are fairly compact.
-
FLAGS == 0 means no saturated objects, no blended objects,
no crowded objects
This catalog is of course useless for scientific purposes.
A visual checks shows no obvious spurious detections and that the coverage
is fairly uniform over most of the field. There are of course
two small strip were no data was taken; see the
the coverage maps at this website.
Comparison with the F22B data shows no shifts over 99.5%
of the area. Unfortunately, this means that small shifts
do exist in 0.5% of the area. The shifts are of the nature desribed
here although smaller in amplitude.
The format of the catalog is:
RA(degrees) Dec(degrees) Mag(3" diameter aperture)
The catalog is found at this site: |