TITLE: GCN CIRCULAR NUMBER: 30245 SUBJECT: GRB 210610B: CrAO/ZTSH continued optical observations and light curve DATE: 21/06/16 22:55:29 GMT FROM: Alexei Pozanenko at IKI, Moscow N. Pankov (IKI, HSE), A. Pozanenko (IKI), V. Rumyantsev (CrAO), S. Belkin (IKI, HSE) report on behalf of IKI GRB FuN: We observed the GRB 210610B (Page et al., GCN 30170) with ZTSH 2.6m telescope of CrAO observatory on June 10,11 (Rumyantsev et al., GCNs 30175, 30178; Pankov et al., GCN 30213) and June 12 - 14. The optical afterglow first reported by UVOT (Page et al., GCN 30170) is clearly detected in each epochs. Some preliminary photometry is following. Date UT start t-T0 Filter Exp. OT err UL(3 sigma) (mid, days) (s) 2021-06-12 20:54:55 2.0545 R 2*120 20.80 0.10 22.2 2021-06-12 22:41:00 2.1282 R 2*120 20.89 0.10 22.8 2021-06-14 20:40:19 4.0649 R 25*120 21.90 0.11 23.3 The photometry is based on calibrations stars reported in (Pankov et al., GCN 30213). Based on our observations in ZTSh on June 10-14, AbAO (Pankov et al., GCN 30243) and photometry reported in GCNs we report the light curve of the afterglow which can be found in http://grb.rssi.ru/GRB210610B/GRB210610B_LC.png After plateau phase lasting up to ~ 0.3 days in R-filter, the LC can be approximated by a single power law with index of -1.6.