TITLE: GCN CIRCULAR NUMBER: 12321 SUBJECT: GRB 110820A: optical upper limit DATE: 11/09/02 14:33:04 GMT FROM: Alina Volnova at SAI MSU Volnova (SAI MSU), E. Litvinenko (UBAI), I. Molotov (Institute of Applied Mathematics), A. Pozanenko (IKI) We observed the field of the Swift GRB 110820A (Troja et al., GCN 12288) with 40-cm telescope ORI-40 of Kitab ISON observatory on Aug. 20 starting on 17:48:45 UT, i.e. 15.5 minutes after the BAT trigger. On the stacked image we do not detect any source within the enhanced XRT error box (Beardmore et al., GCN 12291). The photometry is based on the USNO B1.0 star USNO-B1.0 1603-0160240, (J2000) RA = 22:52:56.89 Dec = +70:18:37.5, assuming R 17.19: Tstart UT, T0+, Filter, Exposure, OT, Upper Limit (3 sigma) (mid, d) (s) 17:48:45 0.01072 R 5*120 n/d 19.2 17:48:45 0.02734 R 28*120 n/d 19.6