GCN Circular 21449

R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres
The Instituto de Astrofisica de Canarias

V. Lipunov, E. Gorbovskoy, V.Kornilov, D.Kuvshinov, N.Tyurina, 
P.Balanutsa,
A.Kuznetsov, V.V.Chazov, D. Vlasenko
Lomonosov Moscow State University,
Sternberg Astronomical Institute, Moscow State University

K. Ivanov, O. Gres, N.M. Budnev, S. Yazev, O. Chuvalaev, V. Poleshchuk
Irkutsk State University

A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov
Kislovodsk Solar Station of the Pulkovo Observatory

V. Yurkov, A. Gabovich, Yu. Sergienko
Blagoveschensk Educational State University, Blagoveschensk


D. Buckley, S. Potter, A. Kniazev, M. Kotze
South African Astronomical Observatory

R. Podesta, Carlos Lopez and F. Podesta
Observatorio Astronomico Felix Aguilar (OAFA)

Hugo Levato and Carlos Saffe
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)

MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in IAC was pointed to the  GRB170810A 25 sec after notice time 
and 45 sec after trigger time at 2017-08-10 22:02:26 UT. On our first (10s 
exposure)  set we  found very bright OT.

Mag: 11.258
Ra: 187.938775
Dec: 3.660714

  The message may be cited.

The observations made on zenit distance = 85 degrees, galaxy latitude b = 
66 degree.
The moon (90 % bright part) is  4 degrees above the horizon. The distance 
between  moon and  object is 169
The sun  altitude  is -27.0 degree.
The object can be observed till sunrise at 2017-08-11 06:32:12.