TITLE: GCN CIRCULAR NUMBER: 8754 SUBJECT: GRB 081230: ROTSE-III Detection of Optical Counterpart DATE: 08/12/30 21:20:41 GMT FROM: Fang Yuan at ROTSE F. Yuan (U Mich), E.S. Rykoff (UCSB), report on behalf of the ROTSE collaboration: ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, responded to GRB 081230 (Swift trigger 338633). The first image was at 20:47:53.4 UT, 700.8 s after the burst (8.4 s after the GCN notice time). The unfiltered images are calibrated relative to USNO A2.0. We detect a 19.1 magnitude, steady source in the XRT error box with coordinates: 02:29:19.35 -25:08:49.22 (J2000), with positional uncertainty of 1" or better start UT mag mlim(of image) ---------------------------------- 20:49:23.0 19.1 19.2 This source is not visible in DSS (second epoch), 2MASS or the MPChecker database. A jpeg image is available at http://www.rotse.net/images/gsb338633_3c021-030_key.jpg Continuing observations are in progress.