GRB 221009A (Swift J1913.1+1946): Mondy optical observations

We observed GRB 221009A (Swift J1913.1+1946) (Swift-BAT detection of Swift J1913.1+1946: Dichiara et al., GCN 32632; Kennea and Williams, GCN 32635; Fermi-GBM detection: Veres et al., GCN 32636; Fermi-LAT detection: Bissaldi et al., GCN 32636, IPN localization: Svinkin et al., GCN 32641) with AZT-33IK telescope of Sayan observatory (Mondy) starting on 2022-10-09 (UT) 14:26:54 and continuing to 15:34:05. We clearly detect the optical afterglow (Dichiara et al., GCN 32632; Lipunov et al., GCN 32634; Perley GCN 32638; Hu et al., GCN 32644). Preliminary photometry of the afterglow at the first image is following Date UT start t-T0 Filter Exp. OT Err. UL(3sigma) (mid, days) (s) 2022-10-09 14:26:54 0.01223 R 120 14.84 0.09 20.8 We observe a monotonic decay in brightness, which can be approximated by a power law with an index of -0.52. The photometry is based on the nearby USNO-B1.0 stars (R2)