![]() Since these 40-day periods are longer than the 29 1/2 day cycle of lunar phases caused by its motion relative to the Sun, there will be at least one full moon (and one lunar eclipse) and at least one new moon (and one solar eclipse) during every eclipse season. There are two such 40-day periods during a roughly 49-week period sometimes referred to as an eclipse year, separated from each other by half that time, and each such period is called an "eclipse season". But during an approximately 40-day long period centered on the direction in space where the plane of the Moon's orbit crosses the plane of the Ecliptic (the Sun's apparent path in the sky as a result of our annual motion around it), the Moon is too close to the Ecliptic to pass above or below the Sun or the Earth's shadow, and we have eclipses of the Sun or Moon. Usually when this happens, the approximately 5 degree tilt of the Moon's orbit relative to the orbital path of the Earth and Moon around the Sun causes the Moon to pass above or below the Sun (at new moon), or above or below the shadow of the Earth (at full moon). Twice during that time the Earth, Moon and Sun are more or less aligned: at new moon, when the Moon is between the Earth and Sun, and at full moon, when the Earth is between the Moon and Sun. When And How Often Eclipses Can Occur: Eclipse SeasonsĪs discussed on the page about The Motion of the Moon, the Moon moves around the Earth once every 27.3 days, but because of the Earth's motion around the Sun during that time, it takes about 29 1/2 days for it to gain a full lap on the eastward motion of the Sun caused by the Earth's orbital motion. When Does The Eclipse Take Place Where You Are?īelow, a modified NASA image summarizing details of the total lunar eclipse of Sep 27 - 28, 2015 Types of Eclipses, and Lunar Eclipses in Particular Pictures of the eclipse will be posted here on the 28th and 29th of September Some full moons are slightly closer to us (as is the one on Sep 27/28, 2015) and therefore look a little bigger and brighter than usual, and others are slightly further from us and therefore look a little smaller and fainter than usual, but all full moons are roughly the same brightness, regardless of whether they involve eclipses or not. Important Note: Unlike solar eclipses, which cannot be safely viewed without very dark filters of special manufacture, lunar eclipses are perfectly safe to look at without any filters, as the moon is never bright enough to pose any danger to your vision.
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