posidonius

Unusually for a lava-flooded walled plain, Posidonius remains a conspicuous object even at full moon - although it changes from a rugged feature, filled with rilles, to a bright ring.

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

Inconstant Moon