These two craters display their differences in age. The bottom (Arzachel) is younger than the middle one (Alphonsus). Note Arzachel’s walls are more rugged, and its central peak better preserved. The length of the wall’s shadows indicate greater height (about 10,000 feet high vs the Alphonsus walls which rise to about 7,000 feet).

12 1/2″ Ritchey-Chretien Telescope with an ST8e, 5X Barlow (.11 sec BW)