Naked Eye Lunar Observing Challenge

As the waxing crescent Moon hangs above the western horizon and mimics the classic smile of Alice in Wonderland's Cheshire cat, the only feature easily discernible to the naked eye is the dark elliptical patch of Mare Crisium. This circular lunar sea is landlocked from the other lunar seas and stands alone near the limb of the Moon. As the Moon's phase advances to first quarter, independent Mare Crisium is joined by the merged form of Mare Serenitatis and Mare Tranquillitatis which combined form the Man-in-the-Moon's right eye.

The naked eye view of the full Moon reveals features which are unseen at lesser phases. The bright, shadowless, full illumination accentuates the contrast between the dark lunar seas and the bright highlands. The pulverized rock blasted out of young craters by the meteor impacts that created them form the circular splash of rays on the southern and western face of the moon. The ray material reflects sunlight back toward its source, the sun. At full Moon, the earth is aligned between the sun and Moon, and thus crater ray systems are brightest during full moon.

One of the first things we see at full moon with the naked eye is the friendly face of the Man-in-the-Moon. Circular Mare Imbrium forms his left eye while Mare Serenitatis and Mare Tranquillitatis combined form his right eye. A number of other lunar seas on the southwestern face of the Moon combine to form the Man-in-the-Moon's mouth, but none are individually recognizable. The bright ray system fanning out from the crater Copernicus on the western face of the Moon is visible as a bright spot. The larger ray system surrounding the crater Tycho appears to cover the southern half of the Moon. The ray streaks focus back to Tycho crater, but the crater itself at the center of the rays is too small to be seen with the naked eye.


National Aeronautics and Space Administration