TITLE: GCN CIRCULAR NUMBER: 30775 SUBJECT: GRB 210610A: Maidanak and AbAO optical observations DATE: 21/09/05 23:23:17 GMT FROM: Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru> S. Belkin (IKI), A. Pozanenko (IKI), O. Burhonov (UBAI), R. Ya. Inasaridze (AbAO), N. Pankov (IKI), V. R. Ayvazian (AbAO), D. Datashvili (AbAO), G. V. Kapanadze (AbAO), Sh. Ehgamberdiev (UBAI) report on behalf of IKI-GRB-FuN: We observed the field of GRB 210610A (Page et al., GCN 30160) with AZT-22 telescope of Maidanak Observatory and AS-32 telescope of Abastumani observatory (AbAO). The optical afterglow (Page et al., GCN 30160; Hosokawa et al., GCN 30161; Xu et a., GCN 30162; Kumar et al., GCN 30163; Lipunov et al., GCN 30166; de Wet et al., GCN 30168; Hosokawa et al., GCN 30169; Sun et al., GCN 30185; Watson et al., GCN 30191; Zheng et al., GCN 30203; Kann et al., GCN 30211; Belkin et al., GCN 30214; Moskvitin et al., GCN 30229; Kann et al., GCN 30232; Siegel et al., GCN 30246) is clearly detected in the stacked images. Preliminary photometry of the afterglow is following. Date UT start t-T0 Filter Exp. OT UL(3sigma) Telescope (mid, days) (s) 2021-06-10 17:57:56 0.14529 R 14*300 19.62 0.03 24.0 AZT-22 2021-06-10 20:24:59 0.23769 R 42*60 20.46 0.25 20.6 AS-32 2021-06-12 16:34:08 2.07494 R 7*300 23.09 0.20 23.5 AZT-22 2021-06-13 16:44:01 3.09049 R 12*300 23.77 0.21 24.4 AZT-22 2021-06-14 17:25:22 4.11920 R 12*300 24.08 0.28 24.4 AZT-22 Photometry is based on the SDSS-DR12 nearby stars (Lupton transformations). SDSS-DR12_id RA DEC R(Lupton) J133717.13+142854.9 204.32139900 +14.48192200 17.0295 J133703.62+142832.7 204.26512000 +14.47576300 17.7239 Using our data in the R filter, it was found that the light curve can be described by a broken power-law with power law indices of -0.82 and -1.39. The break time is 0.23+/-0.17 days. These values are consistent with the result reported by Kann et al. (GCN 30211). The light curve can be found at http://grb.rssi.ru/GRB210610A/GRB210610A_LC.png