GCN Circular 3855

A. Henden (AAVSO/USNO) reports on behalf of the USNO GRB Team:

We have acquired BVRcIc all-sky photometry for 23x23arcmin
fields centered on the coordinates of recent GRB localizations
with the USNOFS 1.0-m telescope on 1 or 2 photometric nights
but with bright moonlight and variable seeing.  Stars brighter
than V=12.0 are saturated and should be used with care.  We have
placed the photometric data on our anonymous ftp site:

ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb050525.dat
ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb050607.dat
ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb050802.dat

The astrometry in these files is based on linear plate solutions
with respect to UCAC2 or USNO-A2.0.  The external errors are usually
200mas or better.  The estimated external photometric error is
about 0.03mag.  Some fields are relatively crowded, and the
large apertures required to handle the variable seeing also
blended some measurements, so choose comparison stars wisely.
We have one additional night for GRB050525 that will be
added when reductions are complete.

As always, you should check the dates on the .dat file prior to
final publication to get the latest photometry.  There is
a README file on the ftp directory to give you information
about the procedures used to calibrate these fields.