Five Day Old Moon‡

The Moon now appears as a broad Waxing Crescent, visible during the afternoon and until late in the evening. It transits the zenith near sunset, so the best observing is soon after twilight, while it is high in the sky and atmospheric distortions minimal.


Key Features to Observe Tonight

Mare Tranquillitatis has come more into the sunlight now as the terminator continues to move westward. At its northern edge, the eastern part of Mare Serenitatis is now revealed. This is the torso of the 'soccer player'. The eastern edge of this huge basin is is crossed by numerous ridges, like a wrinkled skin, such as the Dorsa Smirnov (Serpentine Ridge), an especially vibrant system of dorsa (wrinkle ridges). On the northeastern shore of Serenitatis is the ancient walled plain Posidonius.

South of it, the whole of the Mare Nectaris can now be seen. West of Nectaris lie three stunning ring mountain craters: Theophilus, Cyrillus and Catharina. Theophilus partly obliterates the older, similarly sized Cyrillus. Catharina is the southernmost of the trio, an older crater of about the same size again. Chains such as these were once considered evidence arguing for a volcanic origin of the lunar craters. However, lunar surface samples collected from the Apollo missions indicate that these are the results of impacts.

To the south of Mare Nectaris about one diameter away is the Altai Scarp, still partially in darkness. The scarp wall faces east, and is therefore bright; visit it after the Full Moon, when it will appear as a dark line. Southeast is the crater Piccolomini. The area nearer the southern cusp has many craters which crowd the terminator tonight.


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