What are Lunar X and Lunar V?
Have you heard of Lunar X and Lunar V? They are famous optical features on the moon, visible through telescopes. When the moon’s terminator – or line between light and dark on the moon – is located in just the right place, you can see a letter X and a letter V on the moon’s surface. A sign of an alien visitation? No. Lunar X is a great example of how lighting and topography can combine on a planet or moon to produce a pattern that seems familiar to the human eye.
In reality, the illusion of Lunar X is created by sunlight falling on the rims/ridges between the craters La Caille, Blanchini, and Purbach. The V is caused by light illuminating crater Ukert, along with several smaller craters.
People see Lunar X and Lunar V at each cycle of the moon, but only for a short time. They’re observable for about 4 hours around the first quarter moon phase.
Bottom line: Lunar X and Lunar V are optical features on the moon, visible through a telescope for several hours around the time of the first quarter moon.