TITLE: GCN CIRCULAR NUMBER: 7538 SUBJECT: GRB 080330A: ROTSE-III Detection of Optical Counterpart DATE: 08/03/30 04:04:25 GMT FROM: Brad Schaefer at LSU B. E. Schaefer (Louisiana State) and T. Guver (U Istanbul) report on behalf of the ROTSE collaboration: ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB 080330A (Swift trigger 308041). The first image was at 03:41:39.2 UT, 22.4 s after the burst (7.2 s after the GCN notice time). The unfiltered images are calibrated relative to USNO A2.0. We detect a new object, not visible in the DSS (second epoch), with coordinates: 11:17:04.5 +30:37:24.0 (J2000), with positional uncertainty of 1" or better. This is inside the XRT error box. The object is roughly 17.5 magnitude, and it declined immediately only to rise again to a peak at 16.9 mag roughly ~300 seconds after the burst. A jpeg image is available at http://www.rotse.net/images/gsb308041_3b00_img.jpg Continuing observations are in progress.