September’s top lunar feature to observe
Schickard
Type: Crater
Size: 227km
Longitude/latitude: 55.1˚ W, 44.4˚ S
Age: Older than 3.92 billion years
Best time to see: Five days after first quarter (7–9 September) or four days after last quarter (21–22 August)
Minimum equipment: 10x binoculars
Schickard is an impressive crater located near the Moon’s southwest limb. It lies within a densely packed region of lunar highlands surrounded by a multitude of smaller craters, managing to hold its own by virtue of its variegated floor.
Its appearance is heavily foreshortened thanks to its proximity to the Moon’s edge, a vast walled plain created by an ancient rim surrounding a flat floor pockmarked by numerous craterlets. The largest of these are Schickard A, B and C, which have respective diameters of 14km, 13km and 13km, again heavily foreshortened into an elliptical appearance as seen from Earth.
The floor is variegated, meaning it consists of different coloured regions. The north third appears dark with much of what lies to the south light, save for a patch approximately one-sixth the total area in the southeast. which again appears dark. The three largest interior craterlets all sit within the lighter band.
Schickard has an ancient rim surrounding a flat floor pockmarked by craterlets
Schickard’s rim is remarkably well preserved considering the crater’s age.
The rim boundary is easy to follow except towards the south where things get a little messy, with the southern portion of the rim interrupted by the irregular-shaped and flat-floored crater 32km Schickard E.
A lot of satellite craters are scattered around the rest of the rim. Travelling clockwise from E there are: 17km F, 15km S, 5km D, 7km W, 7km M, 7km L, 12km G, 6km N and 8km X. The 9km crater between N and X is Drebbel N, associated with 30km Drebbel, an irregular-shaped, flat-floored crater to the northeast of Schickard.
To the southeast of Schickard lies a trio of large craters, one of which looks quite odd. The trio are 85km Wargentin, 78km Nasmyth and 114km Phocylides. It’s Wargentin that looks odd, especially when you’re wandering across this area with a low- to midpower eyepiece. The oddness comes from the fact that it looks like it’s lit from the opposite direction to the other craters. This occurs because in its past Wargentin has flooded due to lava forcing up through its floor. However, unlike most other flooded craters, Wargentin has managed to contain its copious amount of invading lava, with the result that it has filled up to the lowest point of its rim. If anything, it resembles more of a flooded plateau than a flooded crater.
Located 320km to the west-southwest of Schickard is 91km Inghirami which looks more like a regular crater. Inghirami is another flat-floored crater, but this time the floor is quite undulating, covered in a multitude of bumps. Estimated to be around 3.9 million years old, like Schickard, Inghirami’s rim has fared well, the crater’s form undisturbed and easy to pick out. Inghirami sits even closer to the Moon’s edge than Schickard and consequently appears even more foreshorted into an elliptical shape. The foreshortening of this area has a big effect on distance here too: it is 320km, centre-tocentre, between Schickard and Inghirami, but they look relatively close together from the perspective of the Earth. For comparison, the north-south dimension of Schickard is unaffected by foreshortening and represents 227km, or 70% of the distance, centre-to-centre, from Schickard to Inghirami.