TITLE:   GCN CIRCULAR
NUMBER:  18890
SUBJECT: GRB 160104A: ISON-Ussuriysk optical observations
DATE:    16/01/18 21:20:20 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

E. Mazaeva (IKI),  E. Chornaya  (UAFO),  A. Matkin (UAFO, ISON), A. 
Volnova (IKI), I. Molotov (KIAM), A. Pozanenko (IKI) report on behalf of 
larger GRB follow-up collaboration:

We observed the field of the GRB 160104A (Melandri  et al., GCN  18815) 
with SANTEL-650 (0.65m)  telescope of UAFO/ISON-Ussuriysk observatory 
starting on 2016-01-04 (UT) 12:21:43. We obtained 60 unfiltered images 
of 60 s exposure. We clearly detect optical afterglow (Guidorzi et al., 
GCN  18816) and preliminary photometry of a combined image is following

Date       UT start  t-T0  Filter  Exp.    OT   OT_err U_limit (3sigma)
                      (mid, days)   (s)

2016-01-04 12:21:43  0.0635 none    59*60  20.45 0.12  22.3


The photometry is based on nearby USNO-B1.0  stars:
USNO-B1.0_id R2
1013-0049708 15.14
1013-0049721 14.90
1013-0049703 16.30
1013-0049714 17.12

We also note the presence of a source  11" South-East of  m = 20.60 +/- 
0.15.