TITLE: GCN CIRCULAR NUMBER: 12646 SUBJECT: GRB 111209A optical limit by "Pi of the Sky" DATE: 11/12/09 23:59:27 GMT FROM: Marcin Sokolowski at Soltan Inst. Nuc Studies,Warsaw M.Sokolowski,A.Majcher,T.Batsch,A.Majczyna,K.Nawrocki,G.Wrochna (NCNR,Swierk), M.Cwiok,W.Dominik,L.W.Piotrowski,A.F.Zarnecki (University of Warsaw), K.Malek,L.Mankiewicz,R.Opiela,M.Siudek,V.Repei (CFT PAN), G.Kasprowicz,M.Zaremba (Warsaw University of Technology), from the "Pi of the Sky" collaboration (http://grb.fuw.edu.pl). The wide field "Pi of the Sky South" apparatus, installed in the private observatory of Alain Maury in San Pedro de Atacama (http://grb.fuw.edu.pl/pi/index.html#spda_site.htm) observed the position of GRB 111209A ( SWIFT trigger #590336 ). Three 10s images of this field have been taken at 01:59:03 - 01:59:51 UT ( 5 hours 13 min 5 sec before the first BAT alert ). No new object can be seen within the error box and the limit on 3 coadded images is 12.7 mag. After receiving the trigger from SWIFT, the field was observed 480 seconds after the GRB. The field has been observed in time period from 7:20:09 to 7:44:25 UT, no new object brighter than 10.2 mag was observed on 10s images. The limit on 20 coadded images is 10.7 mag. Limits are based on the reference star magnitudo in V filter. We acknowladge great support received from Alain Maury at SPdA Observatory.