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Total lunar eclipse visible Dec. 21

The eclipse will begin at 12:32 a.m. on Tuesday in the Central time zone and last three and a half hours.

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The full moon will briefly hide in Earth’s shadow after midnight Tuesday in the Central time zone. The total lunar eclipse will be visible across North America, according to the editors of StarDate magazine.

“This eclipse is going to be a real treat for the whole country,” said Rebecca Johnson of The University of Texas at Austin’s McDonald Observatory. “It’s rare that a total lunar eclipse can be seen from beginning to end, from anywhere in the U.S., from coast to coat.”

View an animation of the eclipse on YouTube.

As Earth’s long shadow falls across the moon, the part in the shadow will turn dark. It will look as though a chunk is missing from the moon. About 70 minutes later, the shadow will completely cover the moon, an event known as “totality.” Next, the shadow will exit the moon’s opposite side. The process will last about three and a half hours total.

“The entire event is going to take a while,” said Johnson, who is also the editor of StarDate magazine. “The most interesting part to me, is watching Earth’s shadow creep across the moon. You can catch that starting about half an hour past midnight in Austin. It’ll take about an hour for the shadow to engulf the moon and turn it blood red.”

The eclipse can be viewed from anywhere in Austin. A dark sky is not necessary as the moon will be very bright. Viewers do not need to worry about having a clear horizon either, as the moon will be almost directly overhead when the eclipse begins and will only drop to about 42 degrees (halfway up the sky).

On average, there are two or three lunar eclipses a year. They occur when the alignment of the sun, Earth, and full moon is just right, so that the moon passes through Earth’s shadow. If the shadow completely engulfs the moon, as in this case, it’s a total eclipse. But if the shadow covers only part of the lunar disk, then it’s a partial eclipse, as occurred in June.

The eclipse begins on December 20 in the Pacific and Mountain time zones, and on December 21 in the Central and Eastern time zones. Time-zone specific information on the eclipse can be found on the StarDate Website.

StarDate magazine is published bi-monthly by the McDonald Observatory, a research unit of the university located in the Davis Mountains of West Texas.

This story originally appeared on StarDate.org.