TITLE: GCN CIRCULAR NUMBER: 17106 SUBJECT: GRB 141121A: three epochs of SAO RAS optical observations DATE: 14/11/27 18:23:54 GMT FROM: Vladimir Sokolov at SAO RAS A.S. Moskvitin and V.N. Komarova report on behalf of a larger team: We observed the field of GRB 141121A (Lien et al., GCN 17075) with the SAO RAS 1-m Zeiss-1000 telescope at three nights: 2014.11.24/25, 25/26, 26/27. The GRB OT (Tanga et al., GCN 17078) is clearly detected in our stacked frames each night. Our charts can be found at ftp://ftp.sao.ru/pub/grb/GRB141121A/GRB141121A_z1000_24_25_26.jpg We used nearby SDSS stars for calibration. The "ugriz" magnitudes were converted to "UBVRI" with the Lupon-2005 equations. Our OT brightness measurements are in good agreement with R-band values estimated within the close epochs and reported in the GCN circulars: Kuroda et al. (GCN 17098), Mazaeva et al. (GCN 17102). Our OT magnitudes are also similar to r-band measurements by Watson et al. (GCN 17100) and Butler et al. (GCN 17101). Our preliminary results are presented in the following table: ----------------------------------------------------- Date T-T0 UT_start-end Exp.,s R_mag ----------------------------------------------------- 24.942 3.782 20:14--00:59 900 20.31+/-0.09 25.956 4.796 22:16--23:38 3600 20.86+/-0.04 26.980 5.820 22:12--00:50 4800 21.36+/-0.09 -----------------------------------------------------