TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5429 SUBJECT: GRB 060805B: optical observation at Sierra Nevada DATE: 06/08/09 16:00:58 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia D. Martínez and A. J. Castro-Tirado (IAA-CSIC Granada), on behalf of a larger collaboration, report: "Following the detection by the IPN of the bright GRB 060805B (Hurley et al. GCNC 5407), we have obtained I-band frames with the 1.5m OSN telescope in Spain starting on Aug 8.04 UT (i.e. 58.3 hr post-burst). Six exposures (300s each) in the I-band filter were taken under non optimum technical conditions. Within the Swift/XRT X-ray afterglow error box (Butler GCNC 5414, Godet et al. GCNC 5428), we only detect a single optical source which is also present in the DSS2 with about the same brightness. The limiting magnitude of our combined I-band image is I = 20.5".