TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3198 SUBJECT: GRB 050408: First Optical observations with TFOSC at the RTT150 DATE: 05/04/09 02:08:11 GMT FROM: Irek Khamitov at TUG Z. Aslan,I. Khamitov,T. Ozisik, K. Uluc(TUG), U. Kiziloglu (METU),I. Bikmaev, R. Gumerov, N. Sakhibullin (KSU/AST), A. Alpar (SabUni), R. Burenin, M. Pavlinsky, R. Sunyaev (IKI), report: We have observed the error box of GRB 050408(GCN 3189 and GCN 3191) with TFOSC (the imaging and spectroscopic camera of the TUBITAK National Observatory, Turkey) attached to the Russian-Turkish 1.5-m telescope (Bakyrlytepe, Turkey). We made series of 30s and 60s exposures in Rc, starting at 18:46 UT. We have found the OT candidate indicated in GCN 3193 getting fainter with a spectral index of -0.63. We have determined its postion and magnitudes using USNO-B1. The position and the preliminary R photometry are as follows: RA: 12:02:17.31 Dec: +10:51:9.4 (+/- 0.1 arcsec)(2000) T-T0(hours) Rc 3.7 20.94 +/- 0.1 4.4 21.05 5.4 21.17 6.7 21.31 8.3 21.50 The reductions are in progress. This message may be cited.