TITLE: GCN CIRCULAR NUMBER: 13820 SUBJECT: GRB 120923A: optical upper limit DATE: 12/09/26 20:24:47 GMT FROM: Alexei Pozanenko at IKI, Moscow L. Elenin (KIAM), A. Volnova (SAI MSU, IKI), I. Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of the Swift GRB 120923A (Yershov et al., GCN 13796) with 0.45-m telescope of ISON-NM observatory starting on Sep. 23 (UT) 05:18:58, i.e 172 s after burst trigger. We took several unfiltered images of 30 s and 60 s exposures. We do not detect the optical counterpart (Levan et al., GCN 13802). A photometry of co-added frames is based on the USNO-B1.0 (R2) nearby stars is following: T0+, Exposure, OT, UL (3 sigma) mid, d (s) 0.00447 9x30 n/d 19.7 0.02839 53x30 n/d 20.5