TITLE: GCN CIRCULAR NUMBER: 15412 SUBJECT: GRB 131030A: SAO RAS optical observations DATE: 13/10/31 10:36:52 GMT FROM: Vladimir Sokolov at SAO RAS A. S. Moskvitin, reports on behalf of SAO RAS GRB follow-up team: We observed the field of GRB 131030A (Troja et al., GCN#15402) with the 1-meter telescope Zeiss-1000 of Special Astrophysical Observatory of RAS in four bands: B, V, Rc, Ic. Observations were started since 23 minutes after the Swift trigger. The weather conditions were excellent, but the air masses of the object was about 3-6. Optical counterpart was clearly detected at all images. Preliminary results of Rc band photometry are as following: T_mid, UT T - T0, h exposure, s R mag +/- error 21:18:45 0.374 60 16.55 +/- 0.02 21:34:05 0.630 60 17.09 +/- 0.03 21:44:14 0.799 120 17.26 +/- 0.02 21:56:27 1.003 120 17.39 +/- 0.03 22:07:26 1.186 120 17.53 +/- 0.03 22:21:30 1.420 360 17.63 +/- 0.02 22:30:08 1.564 480 17.69 +/- 0.03 The magnitudes were calibrated against the set of USNO B1 stars (R2) and not corrected for the Galaxy extinction. Rc band light curve and the first image is shown at ftp://ftp.sao.ru/pub/grb/GRB131030A/GRB131030A_image_LC.jpg