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 insseasins (maria), lowland plains full of dark solidified lava. Several large, bright craters are also seen. At lower centre is Tycho, whose rays of ejected material cover much of the hemisphere. At upper left is bright Copernicus with the slightly fainter Kepler just left and below it. Above and left of these craters is the very bright Aristarchus.