Most craters at this distance from the limb are foreshortened to a width/length ratio of about 2:3. Schiller has an apparent ratio of about 1:5, so can be seen to be extemely elongated. It has been suggested that it is a fusion of two craters, but its perimeter wall appears seamless, and there is no trace of a dividing wall. It is probably the result of several events, but its precise origin remains a mystery.

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

Inconstant Moon