GCN Circular 21044

R.Podesta, C.Lopez, F. Podesta Observatorio Astronomico Felix Aguilar (OAFA) , 
National University of San Juan, Argentina

H. Levato, C. Saffe
Instituto de Ciencias Astronomicas,de la Tierra y del Espacio (ICATE),
San Juan, Argentina

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, D.Kuvshinov, 
A.V.Krylov,  I.Gorbunov, P.Balanutsa, A.Kuznetsov, V.V.Chazov, D. Vlasenko

Lomonosov Moscow State University, Sternberg Astronomical Institut of MSU

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

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

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

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

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

MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in OAFA was pointed to the  GRB170428.38 17 sec after notice time 
and 31 sec after trigger time at 2017-04-28 09:14:14 UT. On our first (10s 
exposure)  set we haven`t found optical transient  within SWIFT error-box 
(ra=330.062 dec=26.9172 r=0.05).
The 5-sigma upper limit has been about 16.5 mag

The observations made on zenit distance = 72 degrees, galaxy latitude b = 
-22 degree.
The moon ( 5 % bright part) below the horizon (The altitude of the Moon is 
-49 degree ).
The sun  altitude  is -24.2 degree.
The object can be observed till sunrise at 2017-04-28 11:06:50

The message may be cited.