Dispersion in stellar interferometry.
The effects of uncompensated dispersion on the fringe visibility in a two beam interferometer are examined for a long baseline stellar interferometer with a path compensator in air rather than in vacuo. We derive a criterion based on the central fringe visibility for evaluating the effects of dispersion and develop a method for selecting suitable compensating media. By limiting the optical bandwidth to ~100 nm and using a compensating system with two glasses it is possible to achieve high fringe visibility in a stellar interferometer with excess air paths of the order of 500 m. The results are generally applicable to other two beam interferometers.
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