Moon Libration

Moon Libration

The left Moon image shows an unfavorable northeastern libration (L:-4.463, B:-5.545) as compared to the right image with a favorable northeastern libration (L:6.979, B:4.707). Notice how close the Endymion crater and the Mare Crisium are to the edge of the Moon in the left image as compared to the right image. Mare Humboldtianum, Mare Marginis and Mare Smythii are not visible in the left image. Also, notice the southeastern Moon edges are about the same.

Libration is the small oscillation of the Moon about its mean position. Longitude libration occurs from the Moon's synchronous rotation and elliptical orbit. Latitude libration is the result of the Moon's equator being slightly tilted (1.5°) from its orbital plane and its orbital plane being tilted 5° from the ecliptic. Diurnal libration is the result of the motion of the observer on Earth as the Earth rotates. When the Moon is rising in the east we see more of the Moon's eastern edge and when the Moon is setting in the west we see more of the Moon's western edge. Maximum librations are 7° 54' longitude and 6° 50' latitude. Also, 1° diurnal libration occures because of motion of the observer as the Earth rotates.

Moon Image on Left Information

Moon Image on Right Information

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