TITLE: GCN CIRCULAR NUMBER: 17750 SUBJECT: GRB 150423A: TSHAO optical observations DATE: 15/04/24 14:37:06 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Mazaeva (IKI), A. Volnova (IKI), A. Kusakin (Fesenkov Astrophysical Institute), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of GRB 150423A (Pagani et al., GCNC 17728) with Zeiss-1000 (East) 1-m telescope of Tien Shan Astronomical Observatory starting on Apr. 23 (UT) 17:43:02. We obtained several images in R-filter. In a combined image we marginally detect the source S2 and do not detect the afterglow (Varela et al., GCN 17729). Coordinates of the S2 (J2000) 14 46 18.94 +12 17 04.4 with an uncertainty of 0.4" is marginally coincide with coordinates reported by Varela et al. (GCN 17729). A preliminary photometry is following date UT start t-T0 Filter Exp. S1 S2 S2_err (mid, days) (s) 2015-04-23 17:43:02 0.57561 R 25*600 >22.7 22.7 0.3 and based on nearby SDSS DR9 stars: SDSS9_id R(Lupton) J144606.22+121513.3 15.42 J144647.40+121502.9 17.54 J144648.52+121523.3 15.15