ten day moon

Tonight's Moon is dominated by two objects, both class 1 ring mountains in the western half of the disc: Copernicus (which became visible last night) about ²/₅ of the way down from the northern cusp, and Tycho (first seen two nights ago) ¹/₅ up from the southern cusp.

To the north of Copernicus the whole of the Mare Imbrium is revealed such that it is easy to appreciate its form. It is for the most part a smooth ellipse bounded by mountain ranges - running clockwise from dark Plato at the north: the Alps, the Caucasus, the Apennines and the Carpathian Mountains - graphically suggesting that the entire basin is the result of a single titanic impact.

On the north-western edge of Imbrium lies the beautiful Sinus Iridium, again a smooth ellipse, ringed by the Jura Mountains and echoing the much larger Mare. The small class 1 crater pleasingly set into the middle of the Juras is Bianchini.

Roughly parallel with the northern edge of Imbrium, the long, thin Mare Frigoris is at last almost fully revealed.

One Crisium length south-south-west of Copernicus in the smooth Oceanus Procellarum is small class 1 Lansberg with its massive mile-thick walls, and continuing half as far again to the south, the Riphaeus Mountains, briefly conspicuous against their bright surroundings.

As far again south from Copernicus, a pair of small, identical rings show bright against the dark background of the Mare Nubium. These class 5 craters are Campanus (to the north-west) and Mercator (to the south-east). Anyone who remembers the Mysterons from their childhood will know exactly what to look for!