TITLE: GCN CIRCULAR NUMBER: 23878 SUBJECT: GRB 190203A: Mondy optical observations DATE: 19/02/06 18:09:10 GMT FROM: Alexei Pozanenko at IKI, Moscow A. Volnova (IKI), E. Klunko (ISTP), A. Pozanenko (IKI), E. Mazaeva (IKI), S. Belkin (IKI) report on behalf of IKI-GRB-FuN: We observed the field of GRB 190203A (Lien et al. GCN 23845) with AZT-33IK telescope of Sayan observatory (Mondy) starting on Feb. 03 (UT) 16:23:21. We detected the optical afterglow (Lien et al. GCN 23845; Moskvitin et al., GCN 23847; Lipunov et al. GCN 23850). Preliminary photometry of the afterglow is following. Date UT start t-T0 Filter Exp. OT Err. UL(3sigma) (mid, days) (s) 2019-02-03 16:23:21 0.04807 R 30*120 21.14 0.27 21.3 The photometry is based on the nearby USNO-B1 stars used in GCN 23847.