Eighteen Day Old Moon‡

Tonight's Waning Gibbous Moon is in the sky throughout the evening, setting near dawn. It transits a few hours after midnight.

 

Key Features to Observe Tonight

What little remains visible of the dark Mare Crisium tonight makes it appear something like a bite taken out of the Moon.

Northwest of the mare, past the prominent and bright crater Proclus, Macrobius appears as a sharp circle. Much farther north, at about the same distance in from the terminator, is Atlas and its close neighbor to the west, Hercules. They show nicely, with good contrast. Tonight will be the final night for observing them this lunation.

South of Mare Crisium, lying mostly below the equator, is the larger Mare Fecunditatis. At its northwest, where it merges with Mare Tranquillitatis, is the crater Taruntius. Its dark flooded floor matches that of the Mare, so only its rim stands out, appearing tonight as a thin, bright ring.

At roughly the same distance from the terminator and further south from Mare Fecunditatis is the nice crater Santbech, with its several related craters.

About the same distance again to the south is the similarly sized crater Rheita. The southwest portion of this crater's rim partly destroys the Rheita Valley. The Rheita Valley is a long, uneven scoop with a slight southeast curve. Its unusual shape is the result of a series of craters which have run together, which give the appearance of a wide valley when viewed under low power. With a telescope of modest power, you should be able to discern several of the individual impact craters which form it.

________________________________________

‡with permission from Lunar Discoverer User's Manual by Robert Duvall, 2013