Dispersion compensation in stellar interferometry.

In long-baseline stellar interferometry, spectrometers are used to disperse starlight for measuring visibility at multiple wavelengths and for fringe tracking with channeled spectra. However, neither prisms nor gratings are well suited to the observation of fringes with wide spectral bandwidths because the mapping from wave number to detector coordinate is nonlinear. The visibility-measurement and fringe-tracking performance are affected by nonlinearity and in many cases it is important to compensate for this. Longitudinal-dispersion correctors may be used to compensate for differential air paths in an interferometer, and we show that these may also be used to correct the nonlinear mapping of a spectrometer.