one day
Viewing the Moon tonight represents a great challenge. Being still so close to the Sun, it is an extremely slender crescent against a bright background, close to the horizon and therefore seen through a considerable thickness of atmosphere. The most favourable conditions will be around the time of the vernal equinox in the northern hemisphere, or the autumnal equinox in the southern hemisphere, when the Moon will be at its greatest angle above the horizon.

Be ready to observe as soon as the Sun sets. Note the point where it disappears below the horizon and look for the Moon around 15 degrees away, above and to the left (northern hemisphere) or right (southern).

It is difficult to be certain which features will be visible tonight. If there was an eclipse at the time of yesterday's new moon, the Sun's light will be falling directly on the eastern side of the Moon, but otherwise the crescent may be centred significantly towards the north or south of the lunar disc. Also, the effects of libration will affect a high proportion of the features on the Moon's thin crescent.

Most prominent of the highly foreshortened craters is the large class 2 walled plain Humboldt, somewhere between the midpoint and halfway to the southern cusp, with the smaller Hecataeus immediately to the north of it, and the still smaller Phillips between its western edge and the terminator. About 1/4 of the length of the terminator north from Hecataeus you may also see the similarly sized Neper, right on the limb and foreshortened to little more than a dark streak. About half as far again north, and itself about half as large, is the old crater Plutarch.