  Gamma-ray bursts are believed to be produced in highly-relativistic
collimated outflows. Support for this comes among others from the association
of the times of detected breaks in the decay of afterglow light curves with the
collimation angle of the jets. An alternative approach to estimate a limit on
the collimation angle uses GRB afterglows without detected prompt-emission
counterparts. Here we report on the analysis of a dedicated survey for the
search of these orphan afterglows using the Wide Field Imager at the 2.2m
MPI/ESO telescope at La Silla, Chile. We monitored ~12 square degrees. in up to
25 nights typically spaced by one to two nights with a limiting magnitude of
R=23. Four previously unknown optical transients were discovered and three of
these associated with a flare star, a cataclysmic variable and a dwarf nova.
The fourth source shows indications for an extragalactic origin but the sparse
sampling of the light curve prevents a reliable classification. We discuss the
results in the context of the collimation of GRBs.
