How often does a lunar eclipse occur?

Answer 1

Lunar eclipses occur about every 6 months, when the Moon passes through the shadow of the Earth. The cycles of the moon's orbit determines whether an eclipse is partial or total.

The maximum number of lunar eclipses that can occur in a calendar year is three, and the maximum number of solar eclipses is 5 (minimum 2). However, these numbers are very rare. On average, there are 1-2 lunar eclipses (partial or total) and 2-3 solar eclipses (partial, annular, or total) each year.

However, during a solar eclipse the Moon's shadow does not cover the entire surface of the Earth (because the Moon is smaller than the Earth). So not everyone on Earth will see the solar eclipse as it occurs. Instead, only those living along the path of the Moon's shadow (called the path of totality) will see it. On the other hand, everyone will be able to see a lunar eclipse. Thus, it is far more common for people to see a lunar eclipse at any given location than a solar eclipse. The average time between two solar eclipses seen from the same location is about 360 years while the average time between two lunar eclipses seen from the same location is between 6 and 12 months.

Twice a year, there is a roughly 38-day window of time during which an eclipse could occur. These windows do not occur at the same time every year, so the term "season" does not refer to a particular time during the calendar year (Spring, Summer, etc.). The two eclipse seasons are separated by just under 6 months. Thus, the complete eclipse cycle lasts for roughly 345 days while the calendar year lasts for 365 days, so the eclipse seasons shift earlier and earlier each year - realigning again every 19 years.

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A lunar eclipse occurs when the Moon passes through the Earth's shadow, which can only occur when the Moon is on the opposite side of the Earth from the Sun - which would normally be when we would see a Full Moon. Therefore, lunar eclipses can only occur during a Full Moon. Similarly, a solar eclipse occurs when the Moon passes in front of the Sun casting its shadow upon the surface of the Earth. This can only occur when the Moon is on the same side of the Earth as the Sun - which would normally be when there is a New Moon. The reason we don't normally get eclipses during Full and New Moons is because the Moon's orbit is tilted with respect to the Earth's orbit. During a Full Moon, the tilted path of the Moon usually takes it above or below the Earth's shadow and thus we get no lunar eclipse and just a normal Full Moon. During a New Moon, the tilted path of the Moon usually makes it such that the shadow of the Moon is cast above or below the surface of the Earth and thus we get no solar eclipse and just a normal New Moon.

However, during the two eclipse seasons the Moon's orbit is titled in such a way that it passes through the Earth's shadow and directly across the line of sight between the Earth and the Sun. If the Moon passes into a Full or New phase during this time an eclipse will occur. If a lunar and solar eclipse occur during the same season, they will be separated by about two weeks (the time it takes for the Moon to move from the opposite side of the Earth to the same side of the Earth as the Sun).

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Another contributor tossed in another 2¢ :

There are between 1 and 4 lunar eclipses per year. Between the years

1901 and 2000, the average was 2.29 of them each year.
It can be anywhere from one to five in a year. During the 100 years

of the 20th Century, they averaged 2.29 per year.

Answer 2

Solar eclipses are fairly numerous, about 2 to 4 per year,

Answer 3

There are between 1 and 4 lunar eclipses per year.

Between the years 777788 the average was 2.29 of them each year.

Answer 4

every 6 months

Answer 5

Typically once or twice a year.