TITLE: GCN CIRCULAR NUMBER: 17718 SUBJECT: GRB 150413A: ISON-Ussuriysk optical observations DATE: 15/04/17 21:33:14 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Mazaeva (IKI), A. Stepura (UAFO, ISON), A. Matkin (UAFO, ISON), A. Volnova (IKI), I. Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of the GRB 150413A (Markwardt et al., GCN 17688) with SANTEL-650 (0.65m) telescope of UAFO/ISON-Ussuriysk observatory sstarting on Apr., 14 (UT) 11:48:05. The afterglow (Ivanov et al., GCN 17689) is clearly detected in a combined image. Preliminary photometry the unfiltered combined image is following Date UT start t-T0 Filter Exp. OT OT_err (mid, days) (s) 2015-04-14 11:48:05 0.95859 none 117*60 20.35 0.15 The photometry is based on nearby USNO-B1.0 stars