Hipparchus (lower left) and adjacent Albategnius are ancient lunar impact craters. North on the Moon is to the left in this picture. Image credit: Marnix PraetHipparchus and Albategnius are a photogenic pair of ancient impact craters lying in the lunar central highlands just to the east of Mare Nubium. Hipparchus is much degraded and modified, due to multiple impacts that have occurred since its formation in the same impact that formed Mare Imbrium some three to four billion years ago. Hipparchus is 160 kilometres (100 miles) wide. Albategnius is a slightly smaller (136 kilometres) but magnificent walled-plain, its walls having huge peaks rising in places 3000-4250 metres (10-14000 feet) above the plain. Its central peak is 1200 metres (4000 feet) high. The smaller craters lying between the two are Halley (centre) and Hind (top), with Klein jutting into Albategniusʼ south-western (lower right) rim. The best time to observe and image the pair is at First and Last Quarter. This nice image was taken by Marnix Praet from Belgium with a ten-inch (250mm) Newtonian fitted with a 3x Televue barlow and a DMK21 camera.
Tethys appears to be peeking out from behind Rhea in this image from the Cassini probe. Scientists believe that Tethys’ surprisingly high albedo is due to the water ice jets emerging from its neighbour, Enceladus.
Mercury attains a greatest easterly elongation of 19 degrees from the Sun on 1 April. This solar separation combined with a favourable inclination of the ecliptic to the western horizon an hour after sunset, means that the period 25 March to around 8 April offers the year’s best evening showing of the innermost planet for Northern Hemisphere observers.
Have you ever seen the Moon hide a star? If you’re an early riser in the UK with a small telescope on Saturday, 24 August 2019 then you can potentially witness the disappearance and reappearance of three naked-eye stars in the Hyades open star cluster of Taurus between 3:40am BST and shortly after sunrise.