TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5183 SUBJECT: GRB 060526: RTT150 optical observations DATE: 06/05/29 05:42:12 GMT FROM: Rodion Burenin at IKI, Moscow I. Khamitov (TUG), I. Bikmaev, N. Sakhibullin (KSU/AST), Z. Aslan (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.), R. Burenin, M. Pavlinsky, R. Sunyaev (IKI) report: We observed the field around position of optical counterpart of GRB060526 (Campana et al. GCN 5162; French & Jelinek GCN 5165; Rykoff et al. GCN 5166) with Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe,TUBITAK National Observatory, Turkey). The observations were made in Rc in two epochs: May 28, 20:07UT and May 29, 00:53UT (~51.64 and ~56.41 hours after the burst). The afterglow is detected clearly in Rc bands in both epochs. We estimate the following Rc magnitudes for the OT: t-t0 m_R err 51.64 21.464 0.04 56.41 21.816 0.05 The last value indicates that the afterglow light curve had returned to the extrapolated power-law decay with index -1.2 which was found between 5 and 16 hours of post-burst reported by Khamitov et al. (GCN 5173), Halpern et al. (GCN 5176) and Cobb et al. (GCN 5180). Our Rc lightcurve can be found at: http://hea.iki.rssi.ru/grb/060526/lc_0528.jpg This message may be cited.