TITLE: GCN CIRCULAR NUMBER: 31837 SUBJECT: GRB 220403B: Kitab optical observations DATE: 22/04/05 21:24:30 GMT FROM: Alexei Pozanenko at IKI, Moscow N. Pankov (HSE), A. Zhornichenko (KIAM), A. Pozanenko (IKI), V. Agletdinov (KIAM), S. Belkin (IKI), Sh. Ehgamberdiev (UBAI) report on behalf of IKI-GRB-FuN: We observed the field of GRB 220403B (Klingler et al., GCN 31820) with Kitab RC-36 telescope in Clear filter. Observation started on April, 03 (UT) 21:23:55 and ended on April, 04 (UT) 00:00:11. We clearly detect the optical afterglow (Klingler et al., GCN 31820; Jelinek et al., GCN 31821; Zhu et al., GCN 31823; Rossi et al., GCN 31826; see also early upper limits in Lipunov et al., GCN 31825; Grossan et al., GCN 31830) in the combined images of an initial part of observations and do not detect it in the final part. Preliminary photometry of the combined images is following Date, UT start, t-T0, Exp., Filter, OT, Err, UL(3 sigma) (mid, days) 2022-04-03 21:23:55 0.05178 40*60 CR 19.24 0.19 20.2 2022-04-03 22:30:39 0.10640 87*60 CR n/d n/d 20.5 The photometry is based on nearby USNO-B1.0 stars, R2 magnitude USNO-B1.0_id R2 1791-0003982 16.77 1791-0003984 17.83