TITLE: GCN CIRCULAR NUMBER: 8584 SUBJECT: GRB 081128A: optical observations DATE: 08/11/30 18:00:48 GMT FROM: Igor Volkov at Asro.Inst.Slovak Acad.Sciences On 2008 November 28 (19:55:36 UT) I began observing the field of GRB 081128A (Margutti et al. GCN Circ. 8571) with the 0.5m reflector and ST-10XME CCD camera of Stara Lesna (Slovak Republic) observatory. Observations consisted of one sequence of 7x300s exposures acquired in standard Rc system. In my coadded frame it was not possible to detect a single source inside the refined XRT error box (Evans et al. GCN Circ. 8573) at the position RA(J2000)=01:23:13.05, Dec(J2000)=+38:07:38.7 with S/N rate more than 5, which corresponds to Rc = 20.7. But on the level S/N = 3 one could measure the object with Rc = 21.6+/- 1.1. So I declare Rc = 20.7 as an upper limit to the source which could be found within error box. The time of the middle of the sequence was 20:10:52 UT. The calibration was performed using the Rc magnitudes of SAO53150 (Scopal A&A 401, L17–L20, 2003) measured just after GRB 081128A observations. The nearby to error box star GSC 2813 1599 = 12.66Rc +/-0.04 from this calibration. This study was supported by the SAI scholarship. Igor Volkov, Astronomical Institute of the Slovak Academy of Sciences, 059 60 Tatranská Lomnica, Slovak Republic; e-mail: volkov@ta3.sk [GCN OPS NOTE(30nov08): This circular was delayed ~17 hrs until the author was added to the vetted list.]