Full Moon. The Moon appears full when it is on the opposite side of the Earth from the Sun during its orbit, when it presents its full sunlit face to Earth. The lunar hemisphere that faces Earth has bright highlands and dark seas, or maria, which are lowland plains full of dark solidified lava. Several large, bright craters are also seen. At upper centre is Tycho, whose rays of ejected material cover much of the hemisphere. At centre right is bright Copernicus with the slightly fainter Kepler just right and above it. Photographed in the northern hemisphere from the Starhome Observatory, California, USA.