TITLE: GCN CIRCULAR NUMBER: 18211 SUBJECT: GRB 150831A: optical upper limit ISON-SSO DATE: 15/08/31 13:02:17 GMT FROM: Alexei Pozanenko at IKI, Moscow L. Elenin (KIAM), A. Volnova (IKI), E. Mazaeva (IKI), I. Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of Swift and INTEGRAL short GRB 150309A (Lien et al., GCN 18209; Mereghetti et al., GCN 18210) with with 0.4-m f/2.4 telescope of ISON-SSO (Siding Spring Observatory) starting on Aug. 31 (UT) 10:44:10 (i.e. 10 minutes after burst trigger). We obtained 30 unfiltered images of 30 s exposure. We do not detect any optical source within XRT error circle (Lien et al., GCN 18209). Preliminary photometry of the filed is following Date UT start t-T0 Filter Exp. UL (3 sigma) (mid, days) (s) 2015-08-31 10:44:10 0.01299 none 30*30 18.8 Photometry is based on nearby USNO-B1.0 stars (R2)