GRB 211023A: Terskol optical observations

We observed the GRB 211023A (Fermi GBM team, GCN 30958) with Zeiss-2000 telescope and Zeiss-600 telescope of Terskol observatory. The afterglow of the GRB 211023A (Lipunov et al., GCN 30977; Kann et al. GCN 30982; Hu et al. GCN 30990; Belkin et al., GCN 31004,31018) is clearly detected with Zeiss-2000 and marginally detected with Zeiss-600. Preliminary photometry of the afterglow is following. Date UT start t-T0 Filter Exp. OT Err. UL. Telescope (mid, days) (s) 2021-10-26 15:08:26 3.11542 R 29*180 20.59 0.16 21.8 Zeiss-2000 2021-10-28 01:06:22 4.51191 R 11*180 20.91 0.10 22.5 Zeiss-2000 2021-10-28 00:15:55 4.47895 R 39*60 20.80 0.40 20.7 Zeiss-600 The photometry is based on the nearby USNO-B1.0 stars RA DEC R2 04:53:23.10336 +85:19:26.4720 14.09 04:52:47.26344 +85:22:52.1508 15.75 The updated light curve can be found in http://grb.rssi.ru/GRB211023A/GRB211023A_LC.png