TITLE: GCN CIRCULAR NUMBER: 15241 SUBJECT: GRB 130903A: optical observations DATE: 13/09/21 19:07:58 GMT FROM: Alexei Pozanenko at IKI, Moscow A. Volnova (IKI), V. Nevskiy (ISON), I. Molotov (KIAM), Yu. Krugly(IA KhNU), I. Slyusarev (IA KhNU), A. Pozanenko (IKI) report on behalf of larger collaboration: After the refined analysis of the ISON-Kislovodsk observations (Volnova et al., GCN 15171) of GRB 130903A field (Mereghetti et al., GCN 15169) in the coordinates of OT reported by Tanga et al. (GCN 15177) we found a faint source with a R magnitude 20.40 ± 0.3. Photometry is based on the stars reported below. We also observed the field of the field with AZT-8 (0.7m) telescope of Institute of Astronomy, Kharkiv National University starting on Sep. 03 (UT) 01:38:52. We took 11 frames with exposures of 120 seconds in R filter. On the stacked image within 1.5 arcmin of error circle localization (Mereghetti et al., GCN 15169) we do not detect any source. Photometry of combined image is the following T_start, T0+, Exp., Filter, UL (3 sigma) (UT) mid (d) (s) 01:38:52 0.03579 11*120 R >20.0 and based on SDSS stars, R (gri -> R transformations by Lupton 2005): # SDSS R Err_R 1 J052835.34-000624.7 15.543 0.013 2 J052817.12-000749.0 14.650 0.012 3 J052841.64-000642.3 14.233 0.013