bright features

There can be no doubt that the focal point of the lunar disc is class 1 Tycho. It is young, formed perhaps 50 million years ago, and its bright ray system extends many hundreds of miles from its position west of centre in the southern hemisphere.

Close to the northern limb, almost directly due north from Tycho, is smaller class 1 Anaxagoras, also with a pronounced ray system. The young crater Thales, due east by two Crisium widths, is smaller still but looks extremely similar.

From here, due south by one Crisium length, is the rayless ring of class 5 Posidonius, on the north-east shore of the Mare Serenitatis. Half-way up Serenitatis, about one Posidonius width in from the western "shore", is the disproportionately bright spot created by the tiny young crater Linne, which is only one mile wide. Up until the middle of the nineteenth century, selenographers using powerful instruments consistently reported a large, well-defined crater, inexplicably at odds with what is currently observable.

To the south of Linne are the striking twins in name - Menelaus, on the southern edge of Serenitatis, and Manilius, to its west-south-west on the northern edge of the Mare Vaporum. Both are bright class 1 craters, roughly 20 miles across and 9000' deep. About one Crisium length south from Menelaus lies the small Dionysius, young and bright in the western end of the Mare Tranquillitatis.

Due east from Menelaus, just between the eastern edge of Tranquillitatis and the western edge of the Mare Crisium is the slightly larger class 1 Proclus. Its ray system spreads to the north and east, but stops abruptly at a strong ray which points back to Posidonius, and another south-south-eastern one which points across a similar distance to the large ring of class 1 Langrenus on the south-eastern edge of the Mare Fecunditatis.

A line south-south-west from Langrenus will, at about two Crisium lengths, pass between a pair of similarly bright points separated by about the length of Langrenus. The north-western one is Stevinus A and the south-eastern one is Furnerius A. Each is about 10 miles across and yet Stevinus A has a ray system which has been traced as far as 650 miles.

Near the centre of the western half of the lunar disc, the glorious class 1 ring mountain Copernicus is the most conspicuous feature after Tycho, and well placed for navigation. To its north by about one Crisium width is small class 1 Pytheas, one of the most reflective areas of the visible surface of the Moon. To its west by about one Crisium length lies smaller class 1 Kepler, and to its north-west the extremely young Aristarchus - the three making a triangle with a right-angle at Kepler, and apparently outlined in rays.

To the west of Kepler, at just under the distance of Copernicus, is small class 1 Reiner. Just to the west of this is Reiner Gamma, a unique bright feature which shows no relief whatsoever, even when examined at close range by lunar probes.

One third of the way along a line from Kepler to Tycho is young class 1 Euclides (Euclid). The brightness of this 10 mile wide crater is enhanced by an even, 30 mile wide ring of bright ejecta.