  We consider theoretically and experimentally the precession of the optical
vortex in a singular beam propagating nearly perpendicular to the crystal
optical axis, the beam and the crystal axis rotating with different angular
velocities. The precession is a result of different scales along the major axes
in a uniaxial crystal. Also we analyze the properties of the optical reducer
consisting of two rotating crystals and a wave retarder between them permitting
us to control the form of the vortex trajectory.
