A supermoon briefly breaks through the clouds over Wantagh on...

A supermoon briefly breaks through the clouds over Wantagh on Sunday, Dec. 3, 2017. Credit: Newsday / Thomas A. Ferrara

Phones at the ready, Instagrammers.

Sunday night brings a supermoon, which can be considered the year’s “first, last and only supermoon,” according to EarthSky.org, a site that offers daily updates on the night sky.

Such a phenomenon occurs, practically speaking, when the moon is full at just about the same time that it’s at perigee — meaning when its monthly elliptical orbit brings it closest in to earth.

Or, as EarthSky.org also points out, Sunday’s can be considered the fourth of the year, if you also count the new moons that come closest to earth, but are not visible from here. That is because new moons line up between earth and the sun, and “the brightness of the Sun outshines the dim Moon,” according to NASA.

As for the moons we can see, being closer to earth can make the full moon appear larger, by as much as 14 percent, than the smallest-looking full moon, according to NASA’s Jet Propulsion Laboratory.

“Keep in mind that a 14 percent increase in the apparent size of something that can be covered with a fingernail on an outstretched arm won’t seem significantly bigger,” the laboratory said.

However, what a viewable supermoon might lack in illusionary size can be partly made up for in brightness, which NASA says “can increase up to 30 percent as a result of the Moon being closer to Earth.”

Even that can be harder to appreciate if observers are in a city or other spots with bright overhead lights, so it’s best to look for a viewing spot where skies are darker.

Moon rise Sunday over Long Island is at 4:56 p.m., said Joe Pollina, National Weather Service meteorologist in Upton, citing the U.S. Naval Observatory, with moon set at 7:47 a.m. Monday.

However there is a 40 percent to 50 percent chance of cloud cover for the entire Island for Sunday into Monday, John Cristantello, a meteorologist with the weather service, said Saturday night. The western part of Long Island will have fewer clouds, he said.

With John-Paul Salamanca

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