The earth will start to pass directly between the moon and sun late Sunday, eventually entering a total eclipse that will make the lunar surface look rusty red, or what’s called a Super Blood Moon.

And this astronomical event is completely safe to watch. No special glasses needed, unlike the last total eclipse of the sun, visible in North America in August 2017.

“When the moon goes total eclipse, it gets a burnt orange or reddish, depending on a number of factors,” said Paul Oswald, president of the South Jersey Astronomy Club. “It’s a little bit different each time. But it’s pretty cool.”

Further, it will be a super moon, meaning the moon’s orbit will bring it as close to the Earth as possible. So, the event melds two somewhat rare astronomical phenomenons into one.

The total eclipse will last from about 11:40 p.m. Sunday, Jan. 20, to 12:45 a.m. Monday, Jan. 21, making it perfect for night owls. However, if you fall asleep, you’ll have to wait until May 26, 2021, for the next total lunar eclipse visible in North America. That’s why many eclipse fans are planning their viewing carefully.

Where to watch

Oswald’s group had planned to gather in an event open to the public at Belleplain State Forest in Woodbine, N.J., which is over an hour’s drive from Philadelphia but, because it is so remote, is a prime place for viewing.

Although, more than 1,400 had expressed interest in the South Jersey Astronomy Club’s viewing event at Belleplain, the event was cancelled due to weather, according to a post on Facebook.

But the eclipse should be viewable. The rain is expected to clear and the National Weather Service is forecasting a mostly clear, but bitterly cold night, with a low around 8 and wind chills as low as -8 given wind gusts from 21 to 32 mph.

Other groups had also planned viewing parties, so it’s best to check their websites or social media accounts if you had planned to attend.

The eclipse will be visible in Philadelphia, though it may not be as vivid due to city lights or obstructions. You don’t have to see the eclipse with an astronomy group, but they usually have experts and amateurs on hand to answer questions and offer viewers glimpses through telescopes.

What is a lunar eclipse?

Just before midnight Sunday, the moon will start to pass through Earth’s shadow. The outer shadow is known as the penumbral zone, which blocks part of the sun’s rays from reaching the moon. Later, the inner shadow, or umbral, enters a zone that blocks all direct sunlight from reaching the moon.

If the Earth had no atmosphere, the moon would simply appear black.

“Because the Earth has an atmosphere, sunlight going through the atmosphere bends to refract a little bit,” said Oswald, 64, a longtime amateur astronomer.

That light will give the moon a reddish color, thus the term blood moon. The exact color will depend on various things that can alter the clarity of the atmosphere, such as volcanic activity, storms, fires, or pollution. But, once the moon is fully in eclipse, surrounding stars should pop.

When a lunar eclipse occurs, those living on the “night” side of Earth see it. About a third of eclipses are only penumbral, and are hard to detect. Another third are partial. The final third are total and are often not viewable on one portion of the Earth or another.

Of course, whether it’s visible depends on the weather. Heavy or partial cloud cover will obscure the eclipse.

When to view

The partial and full stages last more than five hours, according to a NASA chart. However, the full core of the eclipse will last about an hour.

So prime viewing, beginning in the umbral phase, will run from 10:34 p.m. Sunday to 1:51 a.m. Monday.

But the real total eclipse will last from 11:41 p.m. to 12:43 a.m. Peak is at 12:12 a.m., according to NASA.

**This story was corrected to state that the earth passes between the moon and sun during a lunar eclipse.**