Correlation measurement and group delay tracking in optical stellar interferometry with a noisy detector

The use of a noisy detector for group delay tracking and/or correlation measurement in optical stellar interferometry is analysed. Expressions are derived for the signal-to-noise ratio of correlation measurement and the probability of tracking loss in the presence of detector noise. It is shown that such a detector can be suitable for either measurement. For example, the high quantum efficiency of modern charge-coupled devices (CCDs) can offset the readout noise to a large extent, making them a good candidate for use in fringe tracking.