TITLE: GCN CIRCULAR NUMBER: 12033 SUBJECT: GRB 110521A: MASTER synchronous and early optical observations limit DATE: 11/05/21 18:50:06 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs O. Gres, K.Ivanov, V.A.Poleshchuk, S.Yazev, N.M.Budnev, O.Chuvalaev Irkutsk State University V.Krushinski, I.Zalozhnich, A. Popov Ural State University, Kourovka 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 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 GRB110521A (Oates et al., GCN Circ 12031) 32 sec s after notice time and 92 sec after GRB time at 2011-05-21 15:53:03.316 UT. On our first (20s exposure) set we haven`t found optical transient within SWIFT error-box . The 3-sigma upper limit has been about 16.0 mag The Swift erros box was inside FOV of the one of the 2 Very Wide Field Cameras (2x480 square degrees, 2x12 Mpixs). We have images before, during and after GRB . The 3-sigma upper limit has been about 12.0 mag each image (5 s exposition). The data reduction is continued. This message may be cited.