TITLE: GCN CIRCULAR NUMBER: 12050 SUBJECT: GRB 110530A: MASTER OT observations DATE: 11/05/30 18:08:57 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs K.Ivanov, O. Gres, V.A.Poleshchuk, S.Yazev, N.M.Budnev, O.Chuvalaev Irkutsk State University E. Gorbovskoy, V. Lipunov, V.Kornilov, D.Kuvshinov, A.Belinski, N.Tyurina, N.Shatskiy, P.Balanutsa, V.V.Chazov, P.V.Kortunov, A.Kuznetsov, D.Zimnukhov, M.Kornilov, A.Sankovich Sternberg Astronomical Institute, Moscow State University V.Krushinski, I.Zalozhnich, A. Popov Ural State University, Kourovka A. Tlatov, A.V. Parhomenko, D. Dormidontov,V. Senik Kislovodsk Solar Station of the Pulkovo Observatory V.Yurkov, Yu.Sergienko, I.Kudelina Blagoveschensk Educational State University, Blagoveschensk MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Tunka(Siberia) was pointed to the GRB 110530A (D'Avanzo et al, GCN12046) 12 sec s after notice time and 73 sec after GRB time at 2011-05-30 15:32:15.215 UT. On our first (10s exposure) set we haven`t found optical transient within SWIFT error-box. The 5-sigma upper limit has been about 15.2 mag (Polarization + R band). The OT appears at 15:42:14 UT (t_start-t_triger = 673 s, Exp_time=130s). Mag ~18.3 (R). After that we see OT on our images in different filters (R,I,Unfiltered,R+P). 20 min ago (2011-05-30 17:44:42): R ~19.5+-0.5. The reduction is continued. This message may be cited. [GCN OPS NOTE(30may11): Per author's request, the subject line was changed from "110521" to "110530".]