TITLE: GCN CIRCULAR NUMBER: 2798 SUBJECT: GRB041006, optical observation in CrAO DATE: 04/10/12 20:51:02 GMT FROM: Vasilij Rumjantsev at CrAO V.Rumyantsev (CrAO), V.Biryukov (SAI, MSU), A.Pozanenko (IKI) report: We have observed the OT found by G. Da Costa, N. Noel and P.A. Price (GCN2765) of GRB041006 (HETE #3570, M. Galassi, et al. GCN2770) with AT-64 telescope of Crimean Astrophysical Observatory. Several 120 s exposure images in R-band were taken between (UT) Oct.6 17:11 - 22:40 under moderate weather conditions and poor seeing. After inspection only 21 images between Oct.6 (UT)18:33-20:27 is used for further reduction. Additional observation on Oct. 7 reveals no OT. The data reduction against seven USNO A2.0 field stars results to following magnitude of the OT and limiting magnitude for October 7 Mean UT, exposure, mag, S/N Oct 6.81 21x120s 19.35R 3.8 Oct 7.85 64x120s >20.0R 3 We do not apply a possible correction to a brightness of the field stars suggested by D. Fugazza et al. (GCN 2782), A. Monfardini et al. (GCN 2790) and P. Garnavich, X. Zhao, T. Pimenova (GCN 2792). This message may be cited.