TITLE: GCN CIRCULAR NUMBER: 20924 SUBJECT: GRB 170317A: Mondy optical observations DATE: 17/03/20 15:19:06 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Mazaeva (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), A. Volnova (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of GRB 170317A (LaPorte et al., GCN 20885) with AZT-33IK telescope of Sayan observatory (Mondy) starting on March, 18 (UT) 14:57:48. We several images in R-filter. The optical afterglow (LaPorte et al., GCN 20885; Mazaeva et al., GCN 20886; Xin et al., GCN 20888; Mao et al., GCN 20889) is visible in stacked images. Preliminary photometry of the afterglow is following Date UT start t-T0 Filter Exp. OT Err. UL (mid, days) (s) 2017-03-18 14:57:48 1.23738 R 30*120 23.25 0.22 23.6 The photometry is based on nearby USNO-B.10 stars Ref.stars USNO_B1_id R2 1405-0167631 15.69 1404-0169027 16.03 1405-0167512 16.85 1404-0169128 16.25