Airy disk
The central spot in the diffraction
pattern of the image of a star at the focus of a telescope, named after
George Airy. It is surrounded by several fine diffraction
rings (see diffraction pattern)
like the rings around the bull's-eye of a target. The size of the Airy disk,
given approximately in radians by 1.22 times
the wavelength of light times the focal
ratio, is the same for all telescopes of a given size and is less in
instruments of larger aperture. (It is
one of the quirks of astronomy that bigger telescopes produce smaller images
of stars.) In practice, however, atmospheric turbulence, unless compensated
for, results in a false disk that is larger than the Airy disk.
Related category
• OPTICS
AND OPTICAL PHENOMENA
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