Using an optical vortex coronagraph and simple adaptive optics techniques we have made the first convincing demonstration of an optical vortex coronagraph that is coupled to a star gazing telescope. In particular we suppressed by 97% the primary star
of a barely resolvable binary system, Cor Caroli, having an effective angular separation of only 1.4 lambda/D. The secondary star suffered no suppression.
Rankine vortex charateristics of a partially coherent optical vortex are explored using classical and physical optics. Unlike a perfectly coherent vortex mode, the circulation is not quantized. Excess circulation is predicted owing to the wave nature
of the composite vortex fields. Based on these findings we propose a vortex stellar interferometer.
