TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3903 SUBJECT: GRB 050827 : OSN 1.5m optical observations DATE: 05/08/29 17:52:41 GMT FROM: Sergei Guziy at IAA S. Guziy, J. Gorosabel, A.J. Castro-Tirado, V. Casanova, A. de Ugarte Postigo, M. Jelinek, (IAA-CSIC) report: "We have acquired R and I-band images of the GRB 050827 XRT error box (Capalbi et al. GCN Circ. 3899) with the OSN 1.5m telescope. We detect two objects consistent with the 8" radius XRT error circle. The coordinates of the two objects are: Source 1: RA(J2000) = 04:17:08.9 DEC(J2000)= +18:11:57.0 Source 2: RA(J2000) = 04:17:09.6 DEC(J2000)= +18:12:02.0 with a conservative astrometric error of 1.5". Based on the USNO catalog we estimate magnitudes of R=23.7 ± 0.37 and R=23.4 ± 0.26 for S1 and S2, respectively. A finding chart can be found at: http://www.dsri.dk/~jgu/grb050827/FCs/osn.R.gif Further observations are encouraged to check the reliability/variability of the two optical sources. We thank Julius Halpern for making us available his 1.3m MDM telescope images." This message can be cited.