TITLE: GCN CIRCULAR NUMBER: 27851 SUBJECT: GRB 200524A: SAO RAS optical observations DATE: 20/05/29 09:29:23 GMT FROM: Alexei Pozanenko at IKI, Moscow S. Belkin (IKI), A. Moskvitin (SAO RAS), A. Pozanenko (IKI), E. Mazaeva (IKI), A. Volnova (IKI) report on behalf of larger GRB IKI FuN collaboration: We observed GRB 200524A (Dirirsa et al., GCN 27797; Pookalil et al., GCN 27809; Capalbi et al., GCN 27811; Gupta et al., GCN 27818) with Zeiss-1.0 m telescope of SAO RAS observatory in Rc-filter. Optical afterglow discovered by ZTF (Ho et al., GCN 27799) and observed by several observations (Kumar et al., GCN 27800; Rumyantsev et al., GCN 27802; Sanwal et al., GCN 27803; Perley et al., GCN 27805; Kumar et al., GCN 27806; de Ugarte Postigo et al., GCN 27807; Blazek et al., GCN 27810; Ogawa et al., GCN 27813; Izzo, GCN 27817; Belkin et al., GCN 27820; Kuin et al., GCN 27825). Preliminary photometry is following Date UT start t-T0 Filter Exp. OT Err. UL (3sigma) (mid, days) (s) 2020-05-27 21:48:28 3.71143 Rc 2400 22.54 0.20 23.6 2020-05-28 22:17:40 4.73171 Rc 2400 n/d n/d 22.6 The photometry is based on the nearby stars of SDSS DR12 catalog and Lupton' transformation gri -> R.