An Etymological Dictionary of Astronomy and Astrophysics

The angular size of a stellar image for long exposures, as determined by the ratio λ/r₀, where λ is the wavelength and r₀ the typical size of → turbulence patches. → Fried parameter.
The most common seeing measurement is the → full-width at half-maximumof the seeing disk. → Airy disk.

See also: → seeing; → disk.