  We consider quantum enhancement of direct-detection interferometric
measurements to increase telescope resolution. We propose a protocol of
measuring interferometric visibility function using imperfectly entangled
states shared between remote telescopes. We show how errors in visibility
measurement, and in turn, errors in intensity distribution of a distant object
depend on the degree of entanglement of the shared quantum resource. We
determine that these errors are sufficiently small over a wide range of
resource states which makes our technique feasible in practical environments.
