lunar libration


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Related to lunar libration: Lunar orbit, Libration in latitude

lunar libration

[′lü·nər lī′brā·shən]
(astronomy)
The effect wherein the face of the moon appears to swing east and west about 8° from its central position each month. Also known as apparent libration in longitude.
The state wherein the inclination of the moon's polar axis allows an observer on earth to see about 59% of the moon's surface. Also known as libration in latitude.
The small oscillation with which the moon rocks back and forth about its mean rotation rate. Also known as physical libration of the moon.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
(15) Appropriate lighting appeared to play a significant role in detecting a crater in the eyepiece, however Webb noted the state of the lunar libration is also an important consideration, relating Schroter's observation of 1797 March 1 when he observed it 'more distinctly than ever, and in quite a new form, as a real, very deep, and bright crater, with an irregular ring scarcely united to the South and open to the North, with a projection on the East side'.
Westfall also discussed two past ALPO lunar projects that could be resurrected - a "Lunar Meteor Search" originally attempted in 1955-65 to look for lunar meteoroid impact flashes, and the visual search in 1967-70 for "Lunar Libration Clouds" of particles at the Lagrangian [L.sub.4] and [L.sub.5] points of the Earth-Moon system.
This recalls a strange assertion made in On Marvellous Things Seen, a list of fabulous phenomena probably compiled by followers of Aristotle: "The strait between Sicily and Italy grows bigger and smaller according to the moon." If this body of water - the Strait of Messina - is imagined in the lunar mirror, the change in its width could be the result of lunar libration. This apparent rocking of the Moon's disk moves the region alternately toward and away from the limb, causing differing degrees of fore-shortening and producing the described effect.
He concentrated on the poorly mapped lunar limb, observing with his 12 1/2-inch Newtonian during times of favorable lunar libration. These first observations were made from Tumamoc Hill in the Tucson Mountains five miles west of the University of Arizona.