TITLE: GCN CIRCULAR NUMBER: 10362 SUBJECT: GRB 100205A: NOT optical observations DATE: 10/02/05 06:01:21 GMT FROM: Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst D. Malesani (DARK/NBI), D. Xu (WIS and DARK/NBI), J. P. U. Fynbo (DARK/NBI), P. Jakobsson (Univ. Iceland), N. R. Tanvir (Univ. Leicester), J. Lindberg (NOT and Univ. Copenhagen), report on behalf of a larger collaboration: We observed the field of GRB 100205A (Racusin et al., GCN 10361) with the NOT equipped with ALFOSC. Observations were carried out in the R and I bands, starting at 4:58 and 5:16 UT, that is 39 and 58 min after the GRB, respectively. Within the XRT error circle, we do not detect any new source down to limiting magnitudes R > 23.7 and I > 23.2 (assuming R=17.3 and I = 16.8 for the object at RA = 09:25:28.94, Dec = +31:44:20.8). We encourage NIR observations.