When can you see the 'blood moon'?

The first lunar eclipse of 2014 is heading for a sky near you, Monday night into Tuesday's pre-dawn hours. Conditions are perfect to allow most of North and South America to watch the whole 6-hour event, though residents of the northeastern US and Canada will miss the tail end of the show.

You don't need any special equipment to watch a lunar eclipse. Since you're looking at the moon, not the sun, there's nothing to hurt your eyes. Just lie back on a comfortable surface (grass, blanket, lawn chair, sleeping bag) and watch the show. Die-hard observers may want to stay out all night, but the best part of the show will be from about 2 a.m. till 4 a.m. Eastern time, or during the hours around midnight for west coast residents.

Lunar eclipses happen when Earth moves between the moon and the sun, casting a shadow across the surface of the moon. Unlike solar eclipses, which are at totality for only about 15 minutes, lunar eclipses are long, slow events. If you don't want to miss it and kick yourself tomorrow, the most important thing to remember is time. Unlike television, these events won't be rebroadcast at a more convenient time for different time zones. 

Solar and lunar eclipses typically happen a few times each year, says NASA scientist Noah Petro, "when the Earth, the moon, and the sun are in precise alignment."

NASA says the eclipse will start at 4:53 UTC, which is 12:53 a.m. Eastern Daylight Time, and 9:53 p.m. Pacific Daylight Time. At that time, the outer edge of Earth's shadow, known as the "penumbra," will start to move across the face of the moon. This takes about an hour and is hard to see, since the moon is still mostly illuminated. You might notice that the moon looks a little dimmer – maybe a bit smudged – but since the penumbra moves slowly and doesn't block too much light, you may not notice anything happening at all.

Don't worry: The show gets better.

'Quite spectacular and very beautiful'

At 1:58 a.m. EDT, or 10:58 p.m. PDT, the moon will finish passing through the penumbra and begin to enter the "umbra," the full, deep shadow of the Earth. You'll be able to see the slightly curved line of Earth's shadow pushing across the face of the moon, at which point "it looks like the moon disappears into darkness," says Dr. Petro. 

The moon's slow but steady disappearance will take just over an hour. By 3:06 a.m. on the East Coast, or just after midnight on the West Coast, the blackness will completely swallow the moon, allowing you to see the most dramatic part of a total lunar eclipse: the reddened moon.

"When it is completely blocked from the sun," says Petro, "the moon will appear a certain hue of red, which is the projection of all the sunsets on the Earth projected onto the face of the moon. It's going to be quite spectacular and very beautiful." That red hue has prompted some to dub this the "blood moon," though it's no bloodier than any other lunar eclipse. 

"It's a very subtle effect," says Petro, "and if any part of the moon is illuminated in the sun, you can't really see it."

This red phase lasts until 4:24 a.m. EDT (1:24 a.m. PDT), when the moon reaches the far side of the umbra (full shadow) and re-emerges into the penumbra (partial shadow). 

"When the moon comes out of Earth's umbra, it begins to look as we've always seen it: this beautiful, bright grey orb in the sky," says Petro.

The moon will still look a bit smudged as it passes through the other side of the penumbra, over the course of the next hour. At 5:34 a.m. EDT, the moon will begin to pass out of the penumbra, steadily brightening until it is fully clear of Earth's shadow. Those in the northeastern US and eastern Canada will lose the moon below the horizon before it emerges completely out of Earth's shadow, which happens at 6:37 a.m. EDT (3:37 a.m. PDT).

What happens when a solar-powered satellite loses the sun?

Petro's interest in this particular eclipse comes from his role as the deputy project scientist for the Lunar Reconnaissance Orbiter (LRO), a satellite currently orbiting the moon.

The orbiter is solar powered, so the eclipse will have serious implications for the spacecraft. "During the eclipse," says Petro, "the moon and the LRO spacecraft are going to be in darkness for a very long period of time, so the battery won't get recharged." LRO's solar panels measure 14 feet long and 10 feet tall, dwarfing the golf-cart-sized spacecraft.

LRO has stayed on during other lunar eclipses, but its past orbits kept it in Earth's shadow only for a short period. This time, the spacecraft will have to pass through the complete shadow twice before the eclipse ends. 

"The spacecraft will be going straight from the moon's shadow to the Earth's shadow," says Petro.

"We're going to be turning off all the instruments on LRO so we don't drain the battery. We'll be monitoring, real-time, how the battery is doing during the eclipse, but we won't be making any scientific observations during this eclipse. When the spacecraft comes out of the eclipse, the battery will slowly charge back up again, and then we can turn the instruments back on," he says.

While his team is monitoring the spacecraft, Petro urges the rest of us to watch the moon itself, despite the late hour.

"They don't happen all the time," he says. "It really gives you a chance to look at the moon changing."  

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