TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2725 SUBJECT: GRB040916 optical limits 17 min after GRB DATE: 04/09/18 08:41:18 GMT FROM: Grzegorz Wrochna at Soltan Inst.for Nuclear Studies M.Cwiok, K.Kwiecinska, L.Mankiewicz, K.Nawrocki, B.Pilecki, L.W.Piotrowski, G.Pojmanski, R.Salanski, M.Sokolowski, D.Szczygiel, G.Wrochna, on behalf of "Pi of the Sky / ASAS" collaboration http://grb.fuw.edu.pl The central part of HETE FOV containing GRB040916 error box was observed by "Pi of the Sky" apparatus at Las Campanas Observatory for the night of 2004.09.15/16 from 00:20:54 UT (17 min after the GRB) till 09:05:00 UT. 10s exposures were taken continuously with 4s intervals by two CCD cameras. No unknown objects wrt Tycho-2 and GSC catalogues has been observed within the GRB040916 error box. The limiting magnitude is ~11.5m for single frames and ~13.0m for 20 coadded frames. More information at http://grb.fuw.edu.pl/pi/ot/grb040916/