![]() ![]() ![]() By the time the Moon has reached last quarter, however, the typical 50-minute delay has returned.Īt the start of spring, the opposite applies. The Moon may rise as little as 23 minutes later on several nights before and after the full Harvest Moon (at about 42 degrees north latitude), which means extra light at peak harvest time near autumn. Because the Moon’s orbit on successive nights is more nearly parallel to the horizon at that time, its relationship to the eastern horizon does not change appreciably, and the Earth does not have to turn as far to bring up the Moon. The section of the zodiac band in which the full Moon travels around the start of autumn is the section that forms the most shallow angle with the eastern horizon. The result of all this is that the Moon doesn’t rise at the same time everyday.īut around the date of the Harvest Moon, the Moon does rise at about the same time for several days in a row. Why? Remember that the zodiac is the band of constellations through which the Moon travels from night to night. At any one moonrise, the Moon occupies a particular place on the celestial sphere (the great dome of the heavens), but when the Earth turns toward that point 24 hours later, the Moon has moved off to the east about 12 degrees, and it takes an average of 50 minutes longer for the Earth to rotate toward the Moon and for the Moon thus to “rise.” Think of it as a giant Slinky in which each loop, representing one lunar orbit of the Earth, advances the orbit a bit farther along the spiral path. The Moon’s orbital motion (combined with the larger orbit of the Earth around the Sun) carries it farther eastward among the constellations of the zodiac from night to night. If interested, here is more detailed information about the Harvest Moon. (Warning: Scientific explanation below!) It may almost seem as if there are full Moons multiple nights in a row! ![]()
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