TITLE: GCN CIRCULAR NUMBER: 11071 SUBJECT: GRB 100805A: SAO RAS optical observations DATE: 10/08/07 13:47:19 GMT FROM: Vladimir Sokolov at SAO RAS A. S. Moskvitin, T. A. Fatkhullin, V. V. Sokolov, T. N. Sokolova & V. N. Komarova (SAO RAS, Niznijh Arkhyz, Russia), report: We observed the field of the GRB100805A (Hoversten E. A. et al., GCN 11047) with the Zeiss-1000 telescope of SAO RAS, Russia. The observations were carried out in the BVRc bands on Aug. 5.843-6.033 UT. Assuming the magnitudes of the reference USNO-B1.0 star (L.P. Xin et al., GCN 11065) as B = 18.94 and R = 17.41 we estimated the brightness of the GRB100805A optical transient as: B = 22.85 +/- 0.11 R = 21.43 +/- 0.10 Errors are formal and do not include ones of USNO-B1.0 to Johnson-Cousins photometric system transformation. This message may be cited.