Overview

variation


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1 A periodic disturbance in the Moon's celestial longitude caused by changes in the Sun's gravitational attraction as the Moon orbits the Earth. It has an amplitude of 40′ and a period of half a synodic month.

2 The yearly change in the coordinates of a star due to the effects of precession and proper motion; also known as annual variation.

Subjects: Astronomy and Astrophysics.


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