GRB 241030B: SAO RAS optical observations

We observed the field of GRB 241030B (Fermi GBM team, GCN 37980; Klingler et al., GCN 37981; Evans, GCN 37983; Zhao et al., GCN 37984), with the 1-m telescope of SAO RAS equipped with the CCD-photometer. We obtained a series of 300 and 600 sec. Rc images started 15 min after the trigger. The OT (Fu et al., GCN 37985; Odeh et al., GCN 37986) is clearly detected in our frames with the following brightness: R = 19.59 +/- 0.06 (18:49:32--19:00:55 UT, t_mid - T0 = 20.89 min); R = 20.61 +/- 0.07 (19:01:33--19:45:54 UT, t_mid - T0 = 49.39 min). This preliminary photometry is based on nearby PS1 stars (magnitudes converted with Lupton 2005 equations) and not corrected for the Galaxy extinction. Further observations are ongoing.