TITLE: GCN CIRCULAR NUMBER: 13693 SUBJECT: GRB 120811C: optical observations DATE: 12/08/20 15:14:34 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Litvinenko (UBAI), A. Volnova (SAI MSU), I. Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of GRB 120811C (Barlow et al., GCN 13622) with 0.4-m telescope of ISON-Kitab observatory starting on Aug. 11 (UT) 15:53:49. We took several unfiltered images of 30 s exposures. The optical afterglow (Denisenko et al., GCN 13623) is clearly detected in single initial frames. A photometry of some co-added frames is based on the SDSS stars SDSS id RA Dec R J131912.45+621444.3 13 19 12,453 +62 14 44,35 16.63 J131815,89+621830,6 13 18 15,896 +62 18 30,67 16.64 is following: T_start, T0+, Exposure, OT, (UT) mid, d (s) 15:53:49 0.01392 4x30 17,90 +/-0.13 15:56:05 0.01569 5x30 17.95 +/-0.13 15:58:55 0.01841 10x30 18.20 +/-0.10 16:04:35 0.02356 15x30 18.45 +/-0.11 16:13:06 0.03145 25x30 18.40 +/-0.07