TITLE:   GCN CIRCULAR
NUMBER:  21237
SUBJECT: GRB 170607A: ISON/Terskol optical observations
DATE:    17/06/09 18:33:32 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

A. Volnova (IKI),  A. Pozanenko (IKI), V. Agletdinov (KIAM),  E. Mazaeva 
(IKI), A. Mokhnatkin (KIAM),   I. Molotov (KIAM)  report on behalf of 
larger GRB follow-up collaboration:

We observed the field of GRB 170607A (D’Ai et al., GCN 21214) with K-800 
(0.8m) telescope  of ISON/Terskol   observatory starting  on June, 08 
(UT) 23:23:04, about 1 day after the burst onset.  We obtained several 
unfiltered images of 20 s exposure. The optical afterglow (D’Ai et al., 
GCN 21214; Heintz  et al., GCN 21217; Lipunov et al., GCN 21220)  is 
still bright and clearly visible in a combined image. Preliminary 
photometry of the afterglow is following


Date       UT start  t-T0   Filter  Exp.   OT    Err. UL
                      (mid, days)     (s)

2017-06-08 22:21:31 1.01959 CR      128*20 18.50 0.28 18.90


Photometry is based on nearby SDSS DR9 stars
SDSS id                   R_Lupton
J002930.50+091415.3       16.314
J002920.28+091527.1       15.963
J002925.73+091637.7       14.803