TITLE: GCN CIRCULAR NUMBER: 8172 SUBJECT: GRB 080903: Optical afterglow candidate DATE: 08/09/03 03:58:28 GMT FROM: Antonio Deugarte at IAA-CSIC A. de Ugarte Postigo (ESO, Chile), A.J. Castro-Tirado, V. Casanova, J. Gorosabel, M. Jelinek, M. Guerrero (IAA-CSIC, Granada) report on behalf of a larger collaboration: We have observed the field of GRB 080903 (Grupe et al., GCN 8169) using the 1.5m OSN telescope at Sierra Nevada Observatory (Granada) in V, R and I bands begining at 02:30 UT (78 min after the burst). We detect a source of I~21.0 on the edge of the XRT error box at the following coordinates (J2000 +/- 0.5"): R.A.: 05:47:10.08 Dec.: +51:15:50.9 Further observations are ongoing from OSN and NOT to check the colour and variability of this source.