TITLE: GCN CIRCULAR NUMBER: 22463 SUBJECT: GRB 180305A: Mondy optical observations DATE: 18/03/06 17:07:13 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Mazaeva (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), A. Volnova (IKI) report on behalf of of larger GRB follow-up collaboration: We observed the field of LAT/Fermi GRB 180305A (Axelsson, et al., GCN 22457) and Konus-Wind (Svinkin et al., GC 22461) with AZT-33IK telescope of Sayan observatory (Mondy). We obtained several images in R-filter starting on Mar. 06 (UT) 12:35:17. The afterglow candidate (Troja et al., GCN 22460) is clearly detected within XRT/Swift error circle (D'Avanzo et al., GCN 22462). Preliminary photometry is following. Date UT start t-T0 Filter Exp. OT Err. UL (mid, days) (s) 2018-03-06 12:35:17 1.15219 R 30*120 22.69 0.15 23.7 The photometry is based on nearby USNO-B1.0 stars USNO-B1_id R2 1221-0050419 18.60 1221-0050432 16.39 1221-0050407 19.31 Since the source has faded in comparison with the previous observation (Troja et al., GCN 22460) we can confirm the afterglow of GRB 180305A.