DIFFRACTION-LIMITED IMAGING FROM THE GROUND: MEASUREMENT OF STELLAR SPATIAL SPECTRA

Algorithms and computational developments in recent years have yielded suitable techniques for overcoming the resolution limits imposed on conventional astronomical observations by atmospheric turbulence. The Knox-Thompson, triple-correlation, and phase-gradient algorithms are capable of reconstructing the diffraction-limited, complex spatial spectrum of an object from a sequence of short-exposure images. The basic principles of these techniques are reviewed with emphasis on photon-limited operation at visible wavelengths. Practical considerations, magnitude limits, and examples of recent applications are presented.