TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4336 SUBJECT: GRB 051211b: RTT150 optical observations DATE: 05/12/12 11:55:05 GMT FROM: Rodion Burenin at IKI, Moscow I. Khamitov (TUG), I. Bikmaev, R. Zhuchkov, N. Sakhibullin (KSU/AST) Z. Aslan (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.), R. Burenin, M. Pavlinsky, R. Sunyaev (IKI) report: The error box of GRB 051211b (INTEGRAL trig. 2712; Mereghetti et al, GCN4327) was observed with Russian-Turkish 1.5-m telescope (RTT150, Bakyrlytepe, TUBITAK National Observatory, Turkey), starting at Dec. 11, 22:23UT, i.e. 18 min after the burst. Observations were started at zenith distance Z=69 degrees and were continued until the object descended into the clouds near the horizon. We made 30x60s exposures in R. The first 20 images were taken in clear sky but the last 10 images show a variable background because of clouds and bright Moon. We did not find the afterglow candidate reported by Klotz et al. (GCN4328) nor on first 60s image nor on image of 20 co-added good images. At the XRT position (Pagani et al., GCN 4332) we marginally detected only one source near the detection limit of our combined image. The coordinates of this source are: 23:02:42.25 +55:04:53.4 (J2000). The finding chart can be found at: http://hea.iki.rssi.ru/~rodion/GRB/051211b/r.jpg Using USNO-B1 stars we estimate limiting magnitude in our combined image as R=~22.3. This message may be cited.