TITLE: GCN CIRCULAR NUMBER: 22596 SUBJECT: GRB 180404B: MASTER-OAFA OT observation DATE: 18/04/04 09:39:48 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, A.Kuznetsov, V.V.Chazov, A.V. Krylov, I. Gorbunov, D. Vlasenko, D.Zimnukhov, D.Kuvshinov, P.Balanutsa Lomonosov Moscow State University, Sternberg Astronomical Institute, Moscow State University R. Podesta, F. Podesta, C. Lopez, C.Francile Observatorio Astronomico Felix Aguilar (OAFA) H.Levato, C. Saffe Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE) R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias D. Buckley South African Astronomical Observatory O. Gres, N.M. Budnev, Yu.Ishmuhametova Irkutsk State University A. Tlatov, V.Senik, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory A. Gabovich, V. Yurkov, Yu. Sergienko Blagoveschensk Educational State University, Blagoveschensk MASTER-OAFA robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Argentina was pointed to the GRB180404B (LaPorte et al. GCN 22590; Beardmore et al. GCN 22594) 27 sec after notice time and 45 sec after trigger time at 2018-04-04 02:12:29 UT. On our first 10s exposure image with unfiltered mlim=16.5 (5-sigma) we don't found optical transient within SWIFT error-box (ra=53.3792 dec=-50.195 r=0.05 LaPorte et al. GCN 22590) MASTER auto-detection system detected OT with RA,Dec=53.392900; -50.214903 and unfiltered m_OT = 18.4 (automatic reduction) on the summary image with 670s exposition started on 2018-04-04 02:12:29 (mlim=19.7) The message may be cited. ==================================================================== The observations started at zenit distance = 73 degrees, galaxy latitude b = -51 degree. The moon (86 % bright part) is 16 degrees above the horizon. The distance between moon and object is 115 The sun altitude was -46.8 degree.