TITLE:   GCN CIRCULAR
NUMBER:  18556
SUBJECT: GRB 150910A: CrAO optical observations
DATE:    15/11/03 19:13:53 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

V. Rumyantsev (CrAO), E. Mazaeva (IKI),  A. Volnova (IKI), A. Pozanenko
(IKI) report on  behalf of larger GRB follow-up collaboration:

We observed the field of the Swift GRB 150910A (Pagani et al., GCN
18264) with ZTSh telescope of CrAO observatory on Sep. 11 and Sep. 12.
We took several images in R,B-filters of 120 s exposure under good
weather conditions on Sep. 11 and non-optimal weather conditions (mean
seeing of 4") on Sep. 12.

The photometry of the afterglow (Pagani et al., GCN 18264; Zheng &
Filippenko, GCN 18265) is following

Date       UT start,  t-t0     Filter   Exp.    OT    OT_err UL(3sigma)
                       (mid, days)        (s)

2015-09-11 17:56:37   1.3762   R        10*120  21.69 0.12   22.9
2015-09-11 18:18:31   1.4022   B        20*120  22.48 0.15   23.5
2015-09-11 18:39:47   1.4244   R        10*120  21.82 0.10   23.2
2015-09-11 19:22:17   1.4436   B        16*120  22.09 0.10   23.5
2015-09-12 18:04:32   2.3801   R        10*120  n/d   n/a    22.3

The photometry is based on SDSS stars used in GCN 18281 (Mazaeva et al.)