Repost: Understanding last quarter moonPosted: November 18, 2011
Originally posted May 24, 2011.
Last, or third, quarter moon almost gets lost in the shuffle, since it spends most of its time in the sky in the dead of night. From EarthSky.org:
Last quarter moon comes about three weeks after new moon. Now, as seen from above, the moon in its orbit around Earth is at right angles to a line between the Earth and sun. The moon is now three-quarters of the way around in its orbit of Earth, as measured from one new moon to the next.
After this, the moon will begin edging noticeably closer to the sun again on the sky’s dome. Fewer people notice the moon during the day from about last quarter on, because the sun’s glare begins to dominate the moon.