Lunar Craters Theophilus, Cyrillus, and Catharina (evening)

On Thursday evening, April 3, the terminator boundary that separtes the moon’s lit and dark hemispheres will fall just to the left of a trio of large craters named Theophilus, Cyrillus, and Catharina that curve along the western edge of gray Mare Nectaris. You can tell what order the craters were formed in by observing how sharp and fresh Theophilus’ rim appears, and by the way it has partially overprinted neighboring Cyrillus to its lower left (or lunar southwest). Under magnification, Theophilus’ terraced rim and craggy central mountain peak are evident. Cyrillus hosts a trio of degraded central peaks inside a hexagonal rim, while much older Catharina’s peak has been submerged, her edges blurred and her floor overprinted by smaller, more recent craters.