Lunar eclipse will be visible on Long Island — if clouds don't get in way

North and South America will see a red moon, or Blood Moon, in a full lunar eclipse early Friday — but it may be difficult to see on Long Island.

The National Weather Service forecasts partly cloudy skies Thursday night into Friday because of high-pressure systems in the Northeast and low pressure in the Southwest.

"I would say it’s not looking good for viewing," said Bryan Ramsey, a service meteorologist. "Pretty much all of New England is going to be cloudy at that time."

Frederick Walter, a professor of astronomy at Stony Brook University, said the eclipse will begin around 11:57 p.m. Thursday as the moon goes through the center of the Earth’s outer shadow, or penumbra.

By 1 a.m. Friday, the moon enters the umbra, or the planet’s innermost shadow.

Around this time viewers can see a "crescent eating into the moon," Walter said.

The eclipse has full totality around 2:30 a.m., when the moon is directly in line with Earth. Totality will last until around 3:30 a.m., the moon becoming more red over time.

With the right conditions, the eclipse will be visible to viewers in the Western Hemisphere: in the Pacific, the Americas, Western Europe and Western Africa, according to NASA's website. 

No special glasses or equipment are needed.

When an eclipse occurs, Walter said, we do not see complete darkness because some of the sun’s rays shine past Earth's atmosphere. 

"The reason it looks red is that it's being illuminated by light refracted to the Earth's atmosphere," he said.

Colors such as reds and oranges have longer wavelengths and can travel past Earth’s atmosphere, Walter said.

But colors such as blues and violets scatter more easily and are omitted once they hit Earth’s atmosphere, the reason our sky is blue, Walter said.

Lunar eclipses occur quite frequently, as the moon orbits through Earth’s shadow at least once a month.

The next lunar eclipse, also a total, will occur Sept. 7, but will be visible to viewers in the Eastern Hemisphere.