TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3760 SUBJECT: GRB050803: CrAO optical observations, possible OT candidate DATE: 05/08/04 17:27:05 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Pavlenko, Yu. Efimov, A. Shlyapnikov, A. Baklanov, V. Rumyantsev (CrAO), A.Pozanenko (IKI), M. Ibrahimov (MAO) on behalf of larger GRB follow up collaboration report: On August 3, 21:20 (UT) we observed XRT error box (Racusin et al., GCN 3752) of GRB050803 (Band et al., GCN 3748) with 2.6m Shain telescope (CrAO). Within XRT error box we detect the object noted in GCN 3753 (Berger et al.). The magnitude of the object is R = 20.72 +/- 0.22 at mid time August 3, (UT) 21:50 and was calibrated against of USNO B1.0 star 0957-0591541 (R=19.31). Taking into account the I ~ 22 mag at August 4.234 (UT) repored by Berger et al. (GCN 3753)one can suggest that the object is fading and can be considered as possible OT candidate. This message may be cited.