TITLE: GCN CIRCULAR NUMBER: 10821 SUBJECT: GRB 100418A: Maidanak optical observations DATE: 10/06/01 20:31:58 GMT FROM: Alexei Pozanenko at IKI, Moscow A. Volnova (SAI MSU), M. Ibrahimov, R. Karimov (MAO), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of the Swift GRB 100418A (Marshall et al. GCN 10612) with AZT-22 telescope of Maidanak observatory on (UT) Apr. 22 (22:34 -- 23:35) and May 7 (22:49 -- 23:27). The optical afterglow (Marshall et al. GCN 10612, Filgas et al. GCN 10617) is detected in single images on Apr. 22 and in a stacked image on May 7. The photometry of the afterglow based on USNO-B1.0 star 1014-0271368 (RA(J2000) = 17:05:26.42 Dec(J2000)= +11:27:32.9) assuming R=17.32 is following: T0+ Filter, Exposure, seeing, mag. (mid, d) (s) 4.0793 R 11x300 0.7 20.56 +/- 0.02 19.0821 R 6x300 1.3 22.05 +/- 0.25