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(fsky, Fraction Of The Sky)
(fraction of the sky, e.g. what a survey covers)

The abbreviation Fsky (or fsky, for Fraction Of The Sky) is used in describing the target of Surveys, as a fraction of the surface of the Celestial Sphere, as opposed to listing square degrees. Occasionally the term Field of View is also used to indicate the target of a survey. The term is particularly used in Cosmic Microwave Background-related surveys, also being used to describe the region of the sky with a certain observed characteristic in CMB studies.