TITLE: GCN CIRCULAR NUMBER: 6909 SUBJECT: GRB071010B, BVRcIc field calibration DATE: 07/10/13 15:46:46 GMT FROM: Arne A. Henden at AAVSO A. Henden (AAVSO) reports: While the field of GRB071010B has been observed by SDSS, we have also obtained a two-night BVRcIc field calibration using the 35cm robotic telescope at Sonoita Research Observatory. The calibration file has a limiting magnitude around V=18, with good standards brighter than V=16 or so. The file is available at ftp://ftp.aavso.org/public/calib/grb/grb071010b.dat This calibration is based on numerous Landolt standards, and has an external zeropoint error of about 0.02mag. We do not expect at this time to extend this calibration to fainter magnitudes. The AAVSO thanks the Curry Foundation for their continued support of the AAVSO International High Energy Network.