TITLE: GCN CIRCULAR NUMBER: 7519 SUBJECT: GRB080319B: optical observations DATE: 08/03/25 21:41:49 GMT FROM: Alexei Pozanenko at IKI, Moscow Yu. Krugly, I. Slyusarev (Institute of Astronomy of Kharkiv National University), A. Pozanenko (IKI) report on behalf of larger collaboration: We observed the afterglow of GRB080319B (Racusin et al. GCN 7427) with 0.7m telescope of Institute of Astronomy, Kharkiv National Univ. starting on (UT) March 19, 18:20 and continuing to March 20, 02:44. The series consist of continuous observations in R and a few frames were taken in V around (UT) 19:58. The afterglow (Racusin et al. GCN 7427, Holland et al. GCN 7428, Li et al. GCN 7430) is detected in the obtained single images. Preliminary photometry of combined images reveals a possible rapid decline of the light curve between (UT, mid time) 18:25 (R~19.1) and 19:04 (R~19.9) and then light curve flattering toward the end of observation March 20 (UT) 02:00 (R~20.1). The light curve between (UT) 19:00 and 02:39 is close to a constant and not compatible with power law decay index of alpha=1.2. The magnitude of the comparison star is based on SDSS calibration (Cool et al, GCN 7465). The message may be cited.