speckle interferometry

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A technique for detecting detail in celestial objects which are normally too small to be resolved because of the effects of atmospheric seeing. Numerous brief exposures (0.1–0.001 s) are taken at high magnification in a narrow range of wavelengths, each of which yields an image consisting of fine structure called speckles. Each speckle is caused by cells of seeing. The speckles from a close double star, for instance, will contain double structure which is detectable even though it is finer than the overall image size. To determine the detail, a laser beam is passed through the photographic image and focused on to a film. The resulting image contains fringes which reveal the overall structure of the original image. The technique is used to measure close double stars and the diameters of red giant stars.

Subjects: Astronomy and Astrophysics.

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