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The Lunar X (also known as the Werner X) is a clair-obscur effect in which light and shadow creates the appearance of a letter 'X' on the rim of the Blanchinus, La Caille and Purbach craters of the 
The Lunar X (also known as the Werner X) is a clair-obscur effect in which light and shadow creates the appearance of a letter 'X' on the rim of the Blanchinus, La Caille and Purbach craters of the Moon
The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...
.
The X is visible only for a few hours before the first quarter, slightly below the lunar terminator
A terminator or twilight zone is a moving line that divides the daylight, daylit side and the dark night side of a astronomical object, planetary body. The terminator is defined as the locus (mathematics), locus of points on a planet or natural s ...
. Near to the X, the Lunar V is also visible, formed by Ukert crater and several other small craters.
References
External links
*LPOD articles: ** ** ** *APOD articles: ** ** - also includes the Lunar V Orbit of the Moon {{Moon-stub