TITLE: GCN CIRCULAR NUMBER: 7796 SUBJECT: GRB 080603B: BOOTES2/TELMA optical observations DATE: 08/06/03 22:44:26 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia A. J. Castro-Tirado, M. Jelinek, J. Gorosabel (IAA-CSIC Granada), P. Kubánek (GACE, U. Valencia), S. Vitek (CVUT Praha), A. de Ugarte Postigo (ESO Santiago), R. Cunniffe (Cork Univ.), R. Fernández-Muñoz (EELM-CSIC La Mayora), P. Martín-Almendros (Fundación Málaga) and L. Sabau-Graziati (INTA Madrid), report: "We are observing the field of GRB 080603B (Mangano et al. GCN 7794) with the recently installed 60cm robotic telescope BOOTES-2/TELMA in Málaga (south Spain). The first observations (120s each, with the r'-band filter) were obtained starting at 20:31 UT (i.e. 51 min after the onset of the event). We detect the optical afterglow (Rujopakarn et al. GCN 7792, Mangano et al.) with 17.3 mag, based on a preliminary calibration using USNO-A2.0. We also confirm the early plateau phase reported by Klotz et al.(GCNC 7795). From our last frame taken at 22:30 UT we derive a 0.3 mag decay. Further images (in g'r'i'Z filters) are on their way. Spectroscopic observations are encouraged." This message can be quoted.