TITLE: GCN CIRCULAR NUMBER: 31008 SUBJECT: GRB211023A: optical afterglow detection from Konkoly Observatory DATE: 21/10/26 16:18:29 GMT FROM: Jozsef Vinko at Konkoly Observator <vinko@konkoly.hu> J. Vinko, A. Pal, L. Kriskovics, R. Szakats, K. Vida, Zs. Szabo (Konkoly Observatory, Hungary) report: We observed the field of GRB211023A (Fermi GBM team, GCN 30958) with the RC80 robotic telescope at Piszkesteto Station of Konkoly Observatory on 2021 Oct 25 starting at 17:46:47 UT. A series of 5x300 sec. frames were collected through Sloan r'- and i' bands. The optical afterglow (Zhirkov et al., GCN #30977; Kann et al. GCN #30982; Hu et al. GCN #30990; Belkin et al. GCN #31004) was detected on the stacked frames with the following magnitudes, calibrated. via nearby PS1 stars: Date UT-middle t-T0(hr) Exp(s) r'(AB-mag) i'(AB-mag) 2021-10-25 18:07:19 53.03 5x300 20.104 +/- 0.089 19.634 +/- 0.081 We measure the flux decline power-law index as -1.43 +/- 0.03, in accord with. Belkin et al. (GCN #31004).