speckle interferometry


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speckle interferometry

A technique whereby the limit to the resolution of a telescope, imposed not by its design but by atmospheric turbulence (see seeing), may be considerably improved: factors of 50 have been reported. A typical stellar image has, at best, a diameter given by that of the diffraction-limited Airy disk; atmospheric turbulence however causes small continuous erratic movements in image position on a long-exposure photograph, producing a final blurred image enlarged many times. In optical speckle interferometry and its more recent infrared counterpart, many short exposures (10–20 milliseconds) of the object are taken in rapid succession. These freeze the effects of turbulence so that the individual ‘speckles' making up the overall image are distortion-free stellar images: those of supergiants are relatively large, those of binary stars are double. Substantial differences between the speckles of the many short exposures require the application of statistical analysis to the images. This leads to a range of information, including the separation and other properties of close binary stars, often hitherto unresolvable. In addition reconstructions have been achieved of the disks of supergiants, such as Betelgeuse; apparent diameters can thus be measured and large-scale surface details discerned. Very small areas of the Sun have also been studied.

speckle interferometry

[′spek·əl ‚in·tər·fə′räm·ə·trē]
(optics)
The use of speckle patterns in the study of object displacements, vibration, and distortion, and in obtaining diffraction-limited images of stellar objects.
References in periodicals archive ?
Traditionally, astronomers have eliminated some of this blurring in visible-light images by using speckle interferometry, which creates an image composed of many short exposures.
The more adventurous can examine the chapter on speckle interferometry for the amateur.
The equipment was used in a technique called speckle interferometry, developed to help earth-bound astronomers compensate for the shimmering distortion of our atmosphere and employed primarily to distinguish between close-together "point sources' of light such as binary stars or Pluto and its moon Charon.
2-arcsecond resolution of the Sun using speckle interferometry.
Known as speckle interferometry, the technique uses computer analysis of thousands of images taken through a mask with seven pinholes.
A second, comparatively inefficient technique is known as speckle interferometry.
But the Harvard-Smithsonian group's method, known as speckle interferometry, takes a lot of images, sometimes through special masks, as the point of light jumps around.
Gibbard (Lawrence Livermore National Laboratory) turned the 10-meter Keck I telescope toward Titan in June and September 1996 and used a technique called speckle interferometry to assemble an infrared view even clearer than those of the Hubble Space Telescope.
Speckle interferometry is a means of getting around the twinkling caused by turbulence in the earth's atmosphere.
Speckle interferometry with the 4-meter telescope on Kitt Peak indicates that Mira actually has a rather oblong shape (S&T: February 1992, page 130).
Eclipses are important, because in distant Pluto's case, the images -- which by now have been made with a charge-coupled-device camera, speckle interferometry and other techniques--still leave a lot to be desired, so that even the objects' sizes and the separation between them remain uncertain.
Most of what we know about their sizes has come within just the last two decades, through such innovative techniques as radar, stellar-occultation timings, speckle interferometry, and a rare spacecraft flyby.