TITLE: GCN CIRCULAR NUMBER: 18521 SUBJECT: GRB 151027A: SAO RAS optical observations DATE: 15/10/28 23:18:01 GMT FROM: Moskvitin Alexander at SAO RAS A. Moskvitin (SAO RAS, Russia), report on behalf of the larger GRB follow-up team: The field of the GRB 151027A (Maselli et al., GCNC #18478) was observed with the Zeiss-1000, 1 meter telescope of SAO RAS on the October, 28. The observations started 36.3 hours after the trigger. Two series of 300 sec. images in Rc band: 6 frames (16:13:57--16:56:20 UT) and 3 frames (17:32:15--17:50:33 UT) were obtained under the tolerable weather conditions. The OT is clearly detected in the stacked frames: # T_mid-T0,h exp,s R_mag 1 36.612 6 x 300 18.7 +/- 0.1 2 37.717 3 x 300 18.9 +/- 0.1 The photometry is based on nearby USNO-B1 stars proposed by A. Pozanenko (IKI RAS). The observations were provided with the help of the SAO RAS staff: V. Komarov, O. Spiridonova and R. Uklein.