Optical EngineeringSpeckle imaging detector optimization and comparison
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Speckle imaging is a statistical technique for achieving near-diffraction-limited imagery of astronomical objects with ground-based telescopes. The performance of this statistical postdetection processing technique is critically dependent on the signal-to-noise ratio (SNR) of the estimators used for various average spectra, which can be a strong function of detector characteristics. We discuss techniques for maximizing SNR under low-light conditions where so-called "read noise" becomes a factor in CCD detectors, and we derive an optimal exposure time for CCD detection when total viewing time limits the SNR. We also show that a properly optimized CCD can outperform a shot-noise-limited detector, in terms of the SNR, at much lower light levels than without optimization.