two day
The Moon's thin crescent will tonight only be visible for a short while after sunset, low in the west. Although the Sun only illuminates a small part of the Moon as seen from the Earth, an observer on the Moon would see that the opposite is true of the Earth - it would appear almost full. As a result, the dark portion of the Moon receives a good deal of light reflected from the Earth, and it may be possible to see, faintly, much of the detail normally only visible around the time of the full moon. This effect is sometimes called the "old moon in the new moon's arms".

Slightly to the north of the midpoint of the terminator, the eastern half of the Mare Crisium has been revealed. It shows as a smooth area - the contrast between its darkness and the brightness of the surrounding highlands will not become apparent for some nights yet.

Langrenus By a strange coincidence, every prominent crater on tonight's tour is similarly bisected by the terminator. Class 1 Langrenus, due south of Crisium by roughly its length, is named after the 17th century John Langrenus - the only survivor from the system of names which he devised for the very first lunar map in 1645. Vendelinus To the south of it by about its width is the marginally larger Vendelinus, a walled plain with its outline interrupted by smaller and more recent craters. Further south, by a slightly bigger separation, is the larger class 5 ring mountain Petavius, with its massive cluster of central peaks rising far above and dominating its floor. To the north of Crisium by roughly one length is Messala, another walled plain, old and studded by subsequent impacts.