The blurring of a stellar (point-like) image due to turbulence in Earth's atmosphere. Seeing estimates are often given in terms of the full-width in arcseconds of the image at the points where the intensity has fallen to half its peak value. The typical value at a good site is a little better than 1". Amateur astronomers often used the five-point Anontiadi scale, which rates seeing as I (perfect), II (good), III (moderate), IV (poor), and V (very bad).
Related categories OBSERVATIONAL ASTRONOMY
OPTICS AND OPTICAL PHENOMENA
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