The westward movement of the terminator has now revealed half of the Mare Imbrium - visible as a smooth semicircle occupying roughly a quarter of the length of the terminator, between the northern pole and the equator. Its southern edge is bounded by the Apennines, arguably the most spectacular of the lunar mountain ranges, which meet the terminator at the class 1 crater Eratosthenes. On the northern shore of Imbrium lies the distinctive dark circle of Plato, an obvious class 5 object.
Within the Imbrium plain, one third of the way from Eratosthenes to Plato the ejecta of small class 1 Timocharis shows up brightly against the dark backdrop. About one Crisium width to the east-north-east, the smooth-floored ring of class 5 Archimedes echoes the larger and darker Plato. To the north-west, and due south from Plato itself by about one diameter stands Pico, an isolated mountain roughly 15 miles wide.
North of Plato, across the long horizontal ribbon of the Mare Frigoris, is an interesting double crater: the deep class 1 Anaxagoras obliterates the western half of class 5 Goldschmidt. At latitude 77° N, Anaxagoras is just one degree outside the Moon's equivalent of the Arctic circle (in which the Sun can remain above the horizon for a full lunar day). The maximum altitude of the Sun as seen from the lunar surface here is about 25°. The combination of this and the crater's considerable depth mean that the Sun will never clear the its southern rim sufficiently to illuminate the whole of its floor, and it must contain a pool of permanent, freezing darkness. It is in places such as this that NASA's Lunar Prospector probe has recently discovered large quantities water, in the form of cometary ice which has accumulated undisturbed over millions of years. This will form the foundation of the agency's plans to establish a permanent human presence on the Moon.
South-south-east of Eratosthenes by two Crisium lengths is Herschel, class 1 and similar in appearance to Timocharis. Immediately to its south is the northernmost of a chain of three diminishing craters: large class 5 walled plain Ptolemaeus (Ptolemy), and ring mountains, class 5 Alphonsus, and class 3 Arzachel. In 1965 the probe Ranger 9 transmitted a series of spectacular images of Alphonsus before impacting north-east of its centre.
South-west of Arzachel by roughly its diameter lies small class 2 Thebit. The smaller crater which has interrupted its west wall gives it the appearance of a diamond ring. Another Arzachel diameter away, to the west in the smooth Mare Nubium, is the nearly vertical black line of Rupes Recta, a sharp fault with its lower side on the west. In two weeks time, with the Sun on its other side, it will appear white instead.
Set into the southern edge of the Mare Nubium is the old walled plain Pitatus, on the western edge of which is the smaller and similarly old class 5 Hesiodus. There is a breech in their shared wall which, when the morning terminator is nearby, produces the Hesiodus Sunrise Ray - a beam which briefly shines across the floor of the crater. Adjacent to this, to the south, is the still smaller Hesiodus A, an example of an extremely rare double concentric crater, the result of an impact being followed by another, smaller impact on exactly the same spot.
Follow a line from Herschel to Thebit, then continue slightly more than the same distance again to the similarly sized class 1 ring mountain Tycho. It is a modest feature now, but in just a few nights it will become the centre of a huge ray system which will dominate the entire disc of the Moon. By contrast, two diameters to the south-east of Tycho is the massive class 3 Maginus, a 115 mile wide walled plain, its walls still three miles high despite millennia of battering by meteorites... yet by the time Tycho reaches its full glory, the mighty Maginus will have become totally invisible.