TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4064 SUBJECT: GRB 051006: optical observations at Sierra Nevada DATE: 05/10/07 13:55:32 GMT FROM: Alberto Castro-Tirado at LAEFF-INTA A. de Ugarte, A.J. Castro-Tirado, S. Guziy, V. Casanova, M. Jelínek and J. Gorosabel (IAA-CSIC): report: "We have imaged a 7' x 7' region centred on the SWIFT/ BAT error box for GRB 051006 (Norris et al. GCNC 4061) with the 1.5-m OSN telescope at the Observatorio de Sierra Nevada starting on Oct 6.105 UT, i.e. 6.0 hours after the onset of the event) under fair meteorological conditions. Within the SWIFT/XRT error box (Morris et al. GCNC 4062), the co-added I-band image (10 x 300 s exposure time) shows three sources at the following coordinates (J2000): ID RA Dec #1 07 23 13.85 +09 30 28.3 #2 07 23 14.11 +09 30 20.4 #3 07 23 13.61 +09 30 23.7 with 0.4" error. Source 1 is a bright star present in the DSS-2. Source 2 is also present in the DSS-2 (blue). Source 3 is below the detection limit of the DSS-2. Additional observations will continue tonight (if weather permits)."