TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  2216
SUBJECT: GRB030418, BVRcIc field photometry
DATE:    03/05/07 16:31:40 GMT
FROM:    Arne A. Henden at USNO/USRA  <aah@nofs.navy.mil>

A. Henden (USRA/USNO) reports on behalf of the USNO GRB team:

We have acquired BVRcIc all-sky photometry for
a 11x11 arcmin field centered at the coordinates
of the optical transient (Price et al. GCN 2148)
for the HETE burst GRB030418 (H2686; Shirasaki et al. GCN 2210)
with the USNOFS 1.0-m telescope on one marginal night.
Stars brighter than V=13.5 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/grb030418.dat
The astrometry in this file is based on linear plate solutions
with respect to UCAC2.  The external errors are less than 100mas.
Due to drifting smoke from prescribed forest fires, the external
photometric error is potentially larger than normal.  We will
acquire additional photometry in the next week or so to
reduce the external error.

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.