TITLE: GCN CIRCULAR NUMBER: 41859 SUBJECT: GRB 250916A: SAO RAS optical observations DATE: 25/09/17 23:24:23 GMT FROM: Alexander Moskvitin at SAO RAS <mosk@sao.ru> A. Moskvitin, O. Spiridonova (SAO RAS), A. Pozanenko (IKI), A. Ghosh, S. Razzaque (CAPP, University of Johannesburg), Tao An and Yuanqi Liu (Shanghai Astronomical Observatory) report on behalf of GRB follow-up collaboration and IKI-GRB-FuN. We observed the field of the GRB 250916A (Fermi GBM team, GCN 41839; Arya et al., GCN 41843; Cheung et al., GCN 41855) with the 1-m SAO RAS telescope Zeiss-1000 equipped with CCD-photometer. We obtained series of 300 sec. images in BVRcIc bands on September 17, 20:21:44--21:42:59 UT. The OT (Belkin et al., GCN 41847; Mohan et al., GCN 41858) is clearly detected in the individual and stacked frames with the brightness of R = 19.60 +/- 0.02 (t_mid - T0 = 1.3059 days = 31.3419 hours). Preliminary photometry is based on the nearby objects from PanSTARRS (magnitudes converted with Lupton 2005 equations) and has not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/41859. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...