Partial lunar eclipse to be visible over Long Island — if clouds don't get in the way

Long Island will experience a partial lunar eclipse on Tuesday night, during the annual full Harvest Moon.

Frederick  Walter, professor of astronomy at Stony Brook University, said the eclipse will enter Earth’s penumbra, or outer shadow, around 8 p.m. on Long Island. But the eclipse will reach its peak around 10:12 p.m. when it enters the umbra, or the innermost shadow.

According to NASA, the eclipse will also take place during a supermoon, or when a full moon is in its closest orbit to Earth, and appear larger than usual. 

“Unlike a solar eclipse, you don't have to go any place special to see it,” Walter said. “You just need clear skies.”

The National Weather Service said on its website that there is a slight chance of rain Tuesday night, which could prevent views of the eclipse.

Lunar eclipses occur due to an imperfect alignment between the Earth, sun and moon, according to NASA’s website.

During a total lunar eclipse, the moon moves into the inner part of the Earth’s shadow, or umbra. The moon will appear dimly lit, but sunlight passing through Earth’s atmosphere will turn the moon red.

But during a partial lunar eclipse, the moon passes through only part of the Earth’s umbra.

Walter said viewers of Tuesday night’s eclipse will only see a sliver of a shadow — or about 8% maximum — grow across the moon and then recede.

“Eight percent of the moon will be dark, and the rest of the moon will be a little bit darker than normal,” he said. “ .. It won't be terribly spectacular.”

The moon will enter the penumbra, or the Earth’s outer shadow, around 8 p.m. on Long Island. It will then orbit in the umbra, or inner shadow, from around 10:12 p.m. to 11:15 p.m. The eclipse will be over by around 1 a.m., he said.

Jason Cousins, president of the Amateur Observers’ Society of New York, which hosts sky watches and other events year-round on Long Island, will keep his eyes to the sky Tuesday evening. If the skies remain clear, he said he may gather with his fellow amateur astronomers at a local park to watch a sliver of the moon vanish together. Although he said a partial eclipse is "not really something to write home about," he believes the sky's beauty is always worth a peek.

“We’re provided two free artistic pictures every day from nature; we’re afforded a sunrise and a sunset," Cousins said Monday afternoon. "And then anything extra is all part of the fun."

People all around the world will be able to view the partial eclipse at different times depending on their location. NASA says it can be seen from the Americas, Europe and Africa. 

If viewers on Long Island can't see the eclipse due to weather conditions, don’t lose hope, Walter said. Partial lunar eclipses tend to occur frequently throughout the year, although they can only occur during full moons.

There are about 12 or 13 full moons every year, each having their own name, Walter said. Tuesday’s full moon is the annual Harvest Moon, as it is the closest one to the autumnal equinox, which is Sept. 22 this year.

The next total lunar eclipse will take place on March 14. A partial lunar eclipse will take place only a few weeks later, on March 25.

“Let’s hope it doesn’t rain,” Walter said.