twenty-four day moon

At its midpoint, the westward-advancing terminator has now reached class 1 Copernicus. To its north, the huge oval of the Mare Imbrium lies half in darkness. On the north-western shore of Imbrium, the Sinus Iridium is beautifully outlined by the crescent Jura Mountains, with small class 1 Bianchini elegantly positioned at the centre of the arc.

To the south-south-west of Copernicus at about two diameters, class 1 Reinhold shows well. At around twice the distance, the slightly smaller class 1 Lansberg appears as a dark circle with a bright rim and central peak.

Roughly one Humorum width south from here, the Riphaeus Mountains are bright. So too is the halo of ejecta around class 1 Euclides (Euclid), just to the west, and under this illumination the tiny dark circle of the crater itself may be seen.

Just over one Humorum length south-east from Euclides, class 1 Bullialdus is about to be overtaken by the terminator. South from here by about one Humorum width is a pair of similarly sized, dark floored class 5 craters, Campanus, to the west, and Mercator on the East. In this light the symmetry they showed when they first appeared two weeks ago is impaired.

A line drawn from Bullialdus to Mercator, extended by about one Humorum width, will reach Hainzel, a geologically complex structure of three amalgamated craters.