Astronomical seeing
= Astronomical seeing
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= Seeing
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Astronomical seeing is the atmospheric blurring of a stellar image, conventionally expressed as the angular full width at half maximum of its long-exposure <point spread function>, usually in arcseconds. For a large aperture in the ideal Kolmogorov model, it is approximately $0.98\lambda/r_0$ radians, with <Fried parameter> $r_0$.