TITLE: GCN CIRCULAR NUMBER: 6485 SUBJECT: GRB070520B: optical observations DATE: 07/06/02 16:32:32 GMT FROM: Vasilij Rumjantsev at CrAO D. Shakhovskoy, V. Rumyantsev (CrAO), V. Biryukov (CrAO, SAI MSU), A. Pozanenko (IKI) on behalf of larger GRB follow up collaboration report: We observed error box of GRB070520B (Moretti et al., GCN 6425) with AZT-11 (1.25m) telescope of CrAO in R-band under not optimal weather conditions (seeing ~3.6 arcsec) on May 20 between (UT)18:47 and 19:21, i.e. starting 1 hour after burst onset. The weather condition No object is found in a refined XRT error box (Moretti et al., GCN 6438 ). Limiting magnitude of a combined image is based on USANO A2.0: Mid time (UT), Exposure, R_Lim (3sigma) May 20.753 6x300 21.0 The combined image can be found in http://grb.rssi.ru/GRB070520B/GRB070520B_AZT11.gif This message may be cited. [GCN OPS NOTE(02jun07): The binary attachment was removed as well as the diagnostics from MIMEDefang reacting to that binary.]