speckle interferometry

A technique for combating the blurring of star images caused by turbulence in the Earth's atmosphere. Because of this problem, the resolution theoretically possible with a particular telescope is rarely achieved. Speckle interferometry can be used to improve resolution and to measure the diameters of some stars. A number of very-short-exposure images are made, typically for 0.02 second. In these, the image of a star appears to be broken up into a pattern of bright speckles by the bending of the starlight as it passes through turbulent cells in the atmosphere. The speckled pattern changes rapidly, so any longer exposure is blurred. The information contained in the individual speckles of a set of images is combined mathematically to extract details about the star.