0.003 seconds exposure, SBIG ST-8E CCD.
18" f/10.5 Ritchey-Chrétien telescope at prime focus.

Cassini is a large, heavily degraded crater on the north-eastern rim of Mare Imbrium. In the telescope, it appears as a large ring of hills surrounding 2 smaller craters. Once seen it is easily recognised.

In the image above, Cassini is close to the right hand edge. To the east (left) is a pair of large craters, Eudoxus and Aristoteles, while to the north (bottom) the Alpine Valley cuts through the lunar Alps. The isolated mountain to the east of Cassini is Piton.

0.005 seconds exposure, SBIG ST-6 CCD.
16" f/20 refractor at prime focus.