TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3783 SUBJECT: GRB050803: CrAO optical observations, no OT candidate DATE: 05/08/10 17:58:30 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Pavlenko, A. Shlyapnikov, Yu. Efimov, A. Baklanov, V. Rumyantsev (CrAO), A.Pozanenko (IKI), D. Sharapov, M. Ibrahimov, (MAO) on behalf of larger GRB follow up collaboration report: We observed XRT error box (Racusin et al., GCN 3752) of GRB050803 (Band et al., GCN 3748) with 2.6m Shain telescope (CrAO) on August 3 (Pavlenko et al., GCN 3760) and August 4. The object mentioned in GCN 3753 (Berger et al.) is detected in both epochs. We recalibrated our data (Pavlenko et al., GCN 3760) and found the R-magnitude of the object: Mid time Aug.3, (UT)22:02 R = 22.10 +/- 0.10 Mid time Aug.4, (UT)21:41 R = 22.05 +/- 0.05 which is in agreement with photometry reported in GCN 3763 (Burenin et al.). Since no variability of the proposed object is detected it cannot be considered as OT candidate. Meanwhile extended object is detected in the FOV with coordinates RA(J2000)= 23:22:38.73 Dec(J2000)=05:47:12.4 at Aug.3, (UT) 22:02 with R=21.78 +- 0.03 which is not visible on Aug. 4 observations. Detailed analysis shows that it is an asteroid with velocity ~0.005 arcsec/sec toward N-W. The detected asteroid in not presented in the catalogs of Minor Planet Center (http://cfa-www.harvard.edu/cfa/ps/mpc.html). This message may be cited.