The Copernican system - the most recent of the four periods of lunar geological activity - takes its name from this magnificent crater. Impacts during this period, which began about 3.9 billion years ago, are generally much smaller than earlier ones. Copernicus itself represents the upper size limit for craters formed during the last billion years.

Photo: Steve Massey. The full size original of this and other astro video camera images may be seen on his Astronomy Page.

Inconstant Moon