Twenty-Eight Day Old Moon‡

Observing the Moon today requires patience and favorable seasons. The Moon is now very close to the Sun in its orbit, and is an extremely slender crescent against a bright background. All the problems that apply to the one day old Moon apply here also. It will rise in the east very shortly before sunrise, and is unlikely to clear the horizon by more than ten degrees before the Sun emerges. To see it in twilight with best contrast therefore means observing close to the horizon and thus through a considerable thickness of turbulent atmosphere.

The best season is the autumn equinox in the northern hemisphere, or the vernal equinox in the southern hemisphere. This is the time that the Moon's orbital plane will be at it greatest angle above the horizon.

In general, it is difficult to be certain which features will be visible tonight, due to libration effects and the effects of critical angles between the Sun, Moon, and Earth on the narrow crescent.

 

Key Features to Observe Tonight

A nice crater to view tonight is Krafft, which appears very eroded, indicating great age. Pair Krafft up with Cardanus, a much smaller crater further south.

Near the equator, a pair of large craters appear to form the number 8: Hedin and Riccioli. Riccioli is the larger, southern crater noted for its unique two-tone floor: partly dark and partly bright.

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