TITLE: GCN CIRCULAR NUMBER: 18275 SUBJECT: GRB 150910A: SAO RAS optical photometry DATE: 15/09/11 02:06:57 GMT FROM: Moskvitin Alexander at SAO RAS A.S.Moskvitin (SAO RAS), V.P.Goranskij (SAI, Moscow State University), report on behalf of larger GRB follow-up team: We observed the field of the GRB 150910A (Pagani et al., GCN #18264) with the Zeiss-1000, 1-meter telescope of SAO RAS (Russia), equipped with the broadband filters UBVRcIc and EEV 42-40 CCD. The observations started since 10.85 hours after the trigger. We obtained sets of 6 x 300-sec. frames in Rc band three times per September, 10/11 night. The OT (reported by Pagani et al., GCN #18264; Zheng & Filippenko, GCN #18265; Dichiara et al., GCN #18266; Kuroda et al., GCN #18267; Xu et al., GCN #18269; McCauley & Pagani, GCN #18270; Zheng et al., GCN #18273; de Ugarte Postigo et al., GCN #18274) is clearly visible even in single frames. The results of observations are as following. # (T_mid-T0),h exp.,s R_mag time, UT 1. 11.035 6 x 300 20.20 +/- 0.05 19:56:03--20:17:48 2. 13.448 6 x 300 20.57 +/- 0.05 22:15:17--22:48:09 3. 15.739 6 x 300 20.78 +/- 0.05 00:32:30--01:05:46 Photometry is based on nearby SDSS stars (their magnitudes were converted with the Lupon 2005 equations).