A real or apparent libratory motion, like that of a balance before coming to rest.
(astronomy) a real or apparent slow oscillation of a moon or satellite; "the libration of the moon"
Libration is an oscillation in the apparent aspect of a secondary body (such as a planet or satellite) as seen from the primary object around which it revolves.
points: in orbital mechanics, when one large body (e.g., the Moon) is in orbit around another large body (e.g., Earth), there are five points in orbits around the larger body where gravitational forces balance out to enable satellites to be placed where they could not stay if the smaller of the large bodies were not present (also called Lagrangian points, for Joseph Lagrange, the mathematician who developed the theory that predicts their existence)
the small oscillations in the moon’s motion that allow Earth-based observers to see slightly more than half the moon’s surface
A real or apparent oscillatory motion, particularly on the moon. This results in more than half of the moon's surface being revealed to an observer on the earth even though the same side of the moon is always towards the earth.
In astronomy a libration (from the Latin verb libro -are "to balance, to sway", cf. libra "scales") is a very slow oscillation, real or apparent, of a satellite as viewed from the larger celestial body around which it revolves. Used alone, the term usually refers to the apparent movements of the Moon relative to Earth, which can be compared to the rocking of a pair of scales about the point of balance.