Referring to stars, especially as regards observation, measurement, and time-keeping.
Sidereal period: the time it takes a celestial boidy to turn once on its axis or revolve once around its primary, where the movement is measured relative to the position of the stars.
Sidereal time: time measured by the apparent motion of the stars (instead of the solar primary), used by astronomers to point telescopes toward celestial targets.
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Development Notes
Text by M. Alan Kazlev
Initially published on 31 December 2001.