TITLE: GCN CIRCULAR NUMBER: 20226 SUBJECT: GRB 161129A: Mondy optical observations DATE: 16/12/01 17:04:15 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Mazaeva (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), A. Volnova (IKI), I. Korobtsev (ISTP) report on behalf of larger GRB follow-up collaboration: We observed the field of GRB 161129A (Kocevski et al., GCN 20210) with AZT-33IK telescope of Sayan observatory (Mondy) starting on November, 30 (UT) 11:19:53. We obtained several images in R-filter. We detected a source coinsiding with optical afterglow (Mazaeva et al. GCN 20215; Klose et al. GCN 20216; Kuin et al. GCN 20217; Kuroda et al. GCN 20218; Yanagisawa et al. GCN 20223). Preliminary photometry of a combined image is following Date UT start t-T0 Filter Exp. OT Err. UL (mid, days) (s) 2016-11-30 11:19:53 1.19324 R 29*120 21.60 0.17 22.8 Photometry is based on nearby USNO-B1.0 stars USNO-B.1_id R2 1221-0612083 17.30 1221-0612140 19.02