TITLE: GCN CIRCULAR NUMBER: 11045 SUBJECT: GRB 100728B: optical photometry of ISON-NM DATE: 10/08/03 21:25:21 GMT FROM: Alexei Pozanenko at IKI, Moscow A. Volnova (SAI MASU), L. Elenin, I. Molotov (ISON), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of the Swift GRB 100728B (Morris et al. GCN 11009) with 0.45-m telescope Ïf ISON-NM observatory on July 28 (Elenin at al., GCN 11012). The afterglow ( Perley et al. GCN 11007; Morris et al. GCN 11009; Ivarsen et al. GCN 11011) is detectable on each of four images taken between July 28 (UT) 10:45:49 - 11:01:14. A photometry of unfiltered images against SDSS field stars and R-mag obtained with Lupton transformations is following t-t0, filter, exposure, OT (sec) 984 W 300 18.36+/-0.17 1294 W 300 18.93+/-0.22 1603 W 300 18.80+/-0.18 1909 W 300 19.00+/-0.30 Finding chart and SDSS calibration stars can be found at http://grb.rssi.ru/GRB100728B/100728b-refstars.png