The 22nd day of the lunar cycle (4th April), just before the last quarter, presents the best imaging conditions for the delightfully busy scene around the 114-km-wide Albategnius crater in the central lunar highlands. Named after the Muslim astronomer and scientist Muhammad ibn Jabir al-Harrani al-Battani (Latinised as Albategnius), it has a depth of 4400m (about twice the relief as Australia’s highest mountain Mt Kosciuszko). The central peak within Albategnius (just east of the younger Klein crater) rises to 1.5 km elevation above the crater floor. This peak has a tiny relatively fresh crater where a meteorite landed precisely at the very top of the peak. It’s diameter of about 1 mile is sufficiently small to be a good test of your imaging system optics, or the ‘seeing’ conditions on the night, confirming the fantastic seeing that I had in the early hours of Easter Sunday morning. Klein has impacted the western margin of Albategnius, whilst Klein A in turn has impacted the NE rim of Klein.

However, the most interesting features in this field of view are the deep linear scours then trend NNW past the east side of Albategnius and along the west edge of Halley, and can also be seen east of Hind and south of Ptolemaeus (orange labels). These colossal linear scars/grooves are 4-6-km wide zones that were sculpted (torn) out of the lunar crust by the earlier massive Imbrium Basin impact during the LHB (Late Heavy Bombardment of lunar history). These grooves point towards the site (well north of this image) where a ~250-km-wide proto-planet impactor formed the massive Imbrium Basin. The Imbrium impactor was about half the size of Vesta and large enough to be classified as a proto-planet, one of many that roamed the early solar system.

In contrast, Albategnius is younger and much smaller impact.

Skywatcher 8 inch/f5, ASI1600mm Pro, red filter, Stack of 500 sub-frames. Phillip Island, Victoria, 04-04-2021.