TITLE: GCN CIRCULAR NUMBER: 17840 SUBJECT: GRB 150518A: Mondy optical observations DATE: 15/05/21 16:49:28 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Mazaeva (IKI), E. Klunko (ISTP), A. Volnova (IKI), I. Korobtsev (ISTP), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of the MAXI/GSC GRB 150518A (Kawamuro, et al., GCN 17825) with AZT-33IK telescope of Sayan observatory (Mondy) starting on May, 20 (UT) 16:50:47. We obtained several images in R-filter of 120 s exposure. The optical afterglow candidate (Xu et al., GCN 17829) which coincides with SDSS J153648.25+161946.9 galaxy is clearly detected. Photometry of the galaxy is following Date UT start t-T0 Filter Exp. OT Err. (mid, days) (s) 2015-05-20 16:50:47 1.81150 R 20*120 21.22 0.1 Photometry is based on SDSS DR9 stars: SDSS9_id R(Lupton) J153646.11+161904.1 17.65 J153638.21+162002.8 18.41 J153637.55+162040.3 17.10 J153645.59+162055.5 16.35