SACRAMENTO (CBS13) — On Sunday night, we have the opportunity to see a total lunar eclipse. But the weather has to cooperate.

So what is an eclipse and how frequent is it?

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An eclipse is when one celestial body is darkened by another’s shadow. Lunar eclipses occur when the Moon moves into the Earth’s shadow created by Earth. Partial lunar eclipses are fairly common, but total eclipses are a bit hard to come by.

Solar eclipses are the opposite. They occur when the Moon blocks the Sun and are pretty rare.

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Sunday’s total lunar eclipse start at 8:29 p.m. and end at 9:54 p.m., local time.

So will the weather cooperate enough for us to see it? That’s the million-dollar question. According to the National Weather Service, we’ll have mostly clear skies with the greatest possibility of cloud cover over the Sierra. Temperatures in the valley will be between 63 and 78 degrees.

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The next lunar eclipse is the early hours of November 8th. Set the countdown clock now.