TYLER, Texas (KETK) – An almost-total lunar eclipse will be visible before dawn Friday morning.

This will be the longest partial (almost total) eclipse in 580 years (1440), it is said that the eclipse will last just over six hours. Another eclipse of this length is not expected until 2669, another 648 years, according to our affiliate NBC DFW.

What is a lunar eclipse?

(Getty Images)

A lunar eclipse takes place when the earth passes directly between the sun and the moon, leaving the moon in the earth’s shadow. According to NASA, in a total lunar eclipse, the moon falls within the darkest part of the earth’s shadow.

During this particular eclipse, up to 99.1% of the moon’s disk will be within the Earth’s umbra, deeming this an “almost total” lunar eclipse.

Some of the sunlight that passes through the Earth’s shadow reaches the moon’s surface causing the moon to appear orange or reddish.

What is the best time to see the eclipse?

The best time to view the lunar eclipse will be around 3:02 a.m. central time. This is expected to be the peak of the eclipse and the best time to see the moon in its red color. The red color will no longer be visible around 3:20 a.m. Clear skies are in the forecast, so seeing this rare eclipse should not be a problem.

What is special about this eclipse?

This is set to be the longest partial lunar eclipse of the millennium, the entire eclipse is expected to be about three hours and 28 minutes. Although the full length of the eclipse is over three hours, the red color will only be visible for around less than 20 minutes.