TITLE: GCN CIRCULAR NUMBER: 32670 SUBJECT: GRB 221009A/Swift J1913.1+1946: Assy optical afterglow observation DATE: 22/10/10 22:04:05 GMT FROM: Alexei Pozanenko at IKI, Moscow V. Kim (FAI), M. Krugov (FAI), A. Pozanenko (IKI), Y. Aimuratov (FAI), S. Belkin (IKI, HSE), N. Pankov (HSE) report on behalf of GRB IKI FuN: We observed GRB 221009A/Swift J1913.1+1946 (Dichiara et al., GCN 32632; Kennea and Williams, GCN 32635; Veres et al., GCN 32636; Bissaldi et al., GCN 32636; Svinkin et al., GCN 32641; Piano et al., GCN 32657; Pillera et al., GCN 32658; Gotz et al., GCN 32660; Frederiks et al., GCN 32668) with AZT-20 telescope of Assy-Turgen observatory starting on 2022-10-10 (UT) 17:12:51. The observations were carried out sequentially with three images for 30 seconds, in each filter. In stacked images we clearly detect the optical afterglow (e.g. Dichiara et al., GCN 32632; Lipunov et al., GCN 32634; Perley GCN 32638; Hu et al., GCN 32644; Belkin et al., GCN 32645; Kuin et al., GCN 32656). Preliminary photometry of the afterglow is following Date UT start t-T0 Exp. Filter OT Err. UL(3sigma) (mid, days) (s) 2022-10-10 17:12:51 n/a 18*30 r' 18.64 0.03 20.8 2022-10-10 17:14:51 n/a 15*30 g' 20.53 0.11 21.1 2022-10-10 17:21:07 n/a 15*30 i' 17.58 0.01 20.7 2022-10-10 17:24:16 n/a 15*30 z' 16.87 0.05 19.8 The photometry is based on the nearby PS1 stars.