  The optical light of the symbiotic binary BF Cygni during its last eruption
after 2006 shows orbital variations because of an eclipse of the outbursting
compact object. The first orbital minimum is deeper than the following ones.
Moreover, the Balmer profiles of this system acquired additional satellite
components indicating bipolar collimated outflow at one time between the first
and second orbital minima. This behaviour is interpreted in the framework of
the model of collimated stellar wind from the outbursting object. It is
supposed that one extended disc-like envelope covering the accretion disc of
the compact object and collimating its stellar wind forms in the period between
the first and second minima. The uneclipsed part of this envelope is
responsible for the decrease of the depth of the orbital minimum. The
calculated $UBVR_{C}I_{C}$ fluxes of this uneclipsed part are in agreement with
the observed residual of the depths of the first and second orbital minima. The
parameters of the envelope require that it is the main emitting region of the
line H$\alpha$ but the H$\alpha$ profile is less determined from its rotation
and mostly from other mechanisms. It is concluded that the envelope is a
transient nebular region and its destruction determines the increase of the
depth of the orbital minimum with fading of the optical light.
