Although Byrgius is some 17 times the size of Byrgius A, which interrupts the eastern edge of its wall, it is the latter which is conspicuous. The bright ejecta from the young intruder has splashed its larger host and formed a ray system which extends more than 250 miles.

Photo: António Cidadão. His Home Page of Astrophotography includes stereograms, animations, and "Seven Craters a Week" from his forthcoming photographic lunar atlas.

Inconstant Moon