TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3240 SUBJECT: GRB050412: optical limit before and during GRB DATE: 05/04/12 09:14:19 GMT FROM: Grzegorz Wrochna at Soltan Inst.for Nuclear Studies M.Cwiok, K.Krupska, K.Kwiecinska, L.Mankiewicz, K.Nawrocki, B.Pilecki, L.W.Piotrowski, M.Sokolowski, D.Szczygiel, G.Wrochna, on behalf of "Pi of the Sky" collaboration http://grb.fuw.edu.pl The GRB 050412 (GCN 3237) error box was observed by "Pi of the Sky" apparatus at Las Campanas Observatory for most of the night. No new object has been found within the Swift-BAT error box before, during or after the GRB. The limiting magnitude on single exposures (10s) and sums of 20 images is 11m and 11.5m respectively (unfiltered).