TITLE: GCN CIRCULAR NUMBER: 9487 SUBJECT: GRB 090530: RTT150 Optical Observation DATE: 09/06/03 17:47:25 GMT FROM: Solen Balman at METU S. Balman (METU), M. Parmaksizoglu (TUG) Z. Eker (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.) I. Bikmaev, N. Sakhibullin (KSU/AST) R. Burenin, M. Pavlinsky, R. Sunyaev (IKI), report: We observed the field of GRB 090530 (Swift trigger=353567, Cannizzo et al.,2009 GCN Circ. 9438) with the Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe, TUBITAK National Observatory, Turkey) on 30 May starting at 18:30:37.7 UT about 15.2 hours (0.633 d) after the burst using the TFOSC CCD (burst detected at 03:18:18 UT with Swift Burst Alert Telescope(BAT)). Flewelling et al. 2009 GCN Circ. 9439 found the afterglow at 16.0 mag at 03:18:42.7 UT. Calibrating the data against the USNO star at RA = 11:57:41.7, Dec = +26:35:43, Rossi et al. 2009 GCN Circ. 9458 obtain R = (22.2 +-0.2) mag 21.3 hrs after burst. They also found a break in the optical light at around 22 ksec post-burst (see also GCN Circ.9440-9443, 9450-9452, 959, 9466, 9478 for white light and UV photometry). We obtained one 900 sec exposure using the R band filter (Bessell filter). We used the Swift XRT position derived by Breadmore at al. (2009) GCN Circ. 9445 to locate the afterglow candidate. We were able see the source, but unable to calculate a magnitude using PSF photometry with DAOPHOT within MIDAS software performed on the 13.3 by 13.3 arcmin field around the candidate. We find a frame upper limit of R = 21.1+/-0.5 mag at 3 sigma and 21.9+/-0.5 mag at 2 sigma confidence level calculated using the same USNO star mentioned in the above paragraph. This message can be cited.