Third Quarter Moon

The moon will complete three quarters of its orbit around Earth, measured from the previous new moon, on Sunday, December 22 at 5:18 p.m. EST, 2:18 p.m. PST, or 22:18 GMT. At its third (or last) quarter phase the moon is half-illuminated, on its western, sunward side. It will rise around midnight local time, and then remain visible until it sets in the western daytime sky during early afternoon. Third quarter moons are positioned ahead of the Earth in our trip around the Sun. About 3½ hours later, Earth will occupy that same location in space. The week of dark, moonless evenings that follow this phase are ideal for observing fainter deep sky targets.