Digital restoration of an image of Betelgeuse.

Lynds, Worden, and Harvey (1976) have obtained a resolved image of Betelgeuse (a Ori) by adapting the technique of speckle interferometry. In this paper are presented the results of applying a sequence of image restoration procedures to their data. Limited superresolution of a rotationally symmetric image (obtained by angular averaging) is performed first, on the understanding that the true image can be represented by a nonnegative real function mapped onto image space. The zeros of the Fourier transform of the superresolved image are interpreted on the basis of Lynds, Worden, and Harvey's image being distorted by nonlinearity of the recording medium, being band-limited (in its spatial frequencies) by the telescope aperture, and having the form of a multiple convolution. The quantities which are assumed to be convolved together are an idealized limb-darkened image, the (intensity) Airy disk of the telescope, and a point spread function incorporating the degradations introduced by the atmosphere and by the errors which occur when the speckles are superposed upon each other. The zeros give estimates of 0';066 + 0'.'006 for the apparent angular diameter and 0.6 + 0.3 for the limb-darkening coefficient. These results permit the reconstruction of a composite point spread function representing the degradation of Lynds, Worden, and Harvey's image. A restored image is finally obtained by Wiener filtering. Appreciable radial and angular variations in the intensity of the disk of Betelgeuse are found. Subject headings: image processing - interferometry stars: atmospheres - stars: late-type