Bailly is an enormous, highly eroded lunar crater, 298 km (185 miles)
in diameter. It is one of the largest ring-formations on the Moon.
Unfortunately, for the amateur astronomer, Bailly lies on the south-eastern
limb and can only be observed at certain librations and under very favorable conditions. The walls are broken up by many small
craters and rose to over 4,000 meters. There is a wealth of detail on the
floor, including a prominent ridge running north-south and a particularly
prominent pair of secondary craters (A and B). Bailly is a comparatively
recent formation, as it breaks up not only the wall of Bailly itself but
also that of B. Bailly B is extraordinarily deep, being only about 64 km
in diameter but with a depressed interior over4,250 meters below the crest
of its wall. Bailly is named after the French astronomer Jean Bailly.