GCN Circular 31821
M. Jelinek, J. Strobl, R. Hudec, C. Polasek (ASU CAS Ondrejov) report: We observed the position of the Swift-detected GRB 220403B (Klingler et al. GCNC 31820) with the D50 telescope of the Astronomical Institute Ondrejov, near Prague, Czech Republic. Our observation started at 21:04 UT, i.e. 22 min after the initial trigger and was performed without a filter. We detect the optical afterglow (Klingler et al. GCNC 31820) in a combined image with exp. mean time 31.3 min after trigger (exposed 21:05--21:22UT) with an AB magnitude RC = 19.02 +/- 0.04.