Self-calibrating shift-and-add technique for speckle imaging

An image-reconstruction technique for astronomical speckle interferometric data is described. This variant of the shift-and-add algorithm originally developed by Lynds et al. [ Astrophys. J.207, 174 ( 1976)] utilizes a weighted impulse distribution of speckle positions to extract an average speckle for a data set. This is done by means of a weighted deconvolution procedure, similar in form to a Weiner filter, which deconvolves the specklegram by the impulse distribution. Results show that this method appears to be self-calibrating for seeing effects. It yields point-spread functions, for observations of an unresolved star, that compare quantitatively with computed Airy patterns for both simple apertures and the fully phased multiple mirror telescope array. Images of the resolved object Alpha Orionis show evidence of an extended stellar envelope.