TITLE: GCN CIRCULAR NUMBER: 20011 SUBJECT: GRB 161004A: refined analysis of TSHAO optical observations DATE: 16/10/07 23:58:37 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Mazaeva (IKI), I. Reva (Fesenkov Astrophysical Institute), A. Kusakin (Fesenkov Astrophysical Institute), A. Volnova (IKI), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We present a refined analysis of our observations (Mazaeva et al., GCN 19980) of the field of GRB 161004A (Evans et al., GCN 19979) with Zeiss-1000 (East) 1-m telescope of Tien Shan Astronomical Observatory. We obtained several images in R filter starting on Oct. 04 (UT) 13:36:52. In a combined image of the first 30 minutes of our observations we detect the afterglow (Breeveld et al., GCN 19984). Preliminary photometry of a combined image is following Date UT start t-T0 Filter Exp. OT Err. UL (mid, days) (s) 2016-10-04 13:36:52 0.03632 R 9*180 21.65 0.25 21.7 Photometry is based on nearby SDSS-DR9 stars used in GCN 19980.