TITLE: GCN CIRCULAR NUMBER: 30229 SUBJECT: GRB 210610A: SAO RAS optical observations DATE: 21/06/13 13:22:59 GMT FROM: Moskvitin Alexander at SAO RAS A. S. Moskvitin and O. A. Maslennikova (SAO RAS), report on behalf of the GRB follow-up team. We observed the field of the GRB 210610A (Page et al., GCN #30160) with the SAO RAS 1-m telescope Zeiss-1000 + CCD-photometer in Rc band on June 11 and 12. We clearly detected the GRB OT (Page et al., GCN #30160; Hosokawa et al., GCNs #30161, #30169; Xu et al., GCN #30162; Kumar et al., GCN #30163; Zhu et al., GCN # 30164; Lipunov et al., GCN #30166; de Wet et al., GCN #30168; Horiuchi et al., GCN #30169; Sun et al., GCN #30185; Watson et al., GCN #30191; Dutta et al., GCN #30200; Zheng et al., GCN #30203, Kann et al., GCN #30211; Belkin et al., GCN #30214) in the stacked frame obtained on June 11 and marginally detected the object in the stacked frame obtained on June 12. Date UT_start UT_end Exp., s T_mid-T0, d R mag June, 11 20:12:02--21:08:03 8 x 300 1.23356 22.43 +/- 0.14 June, 12 19:46:09--21:08:36 12 x 300 2.22477 23.3 +/- 0.3 The preliminary photometry is based on magnitudes of the nearby SDSS stars (transformed with the Lupton 2005 equations). The OT magnitudes were not corrected for MW extinction.