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Shine On, Harvest Supermoon: How to See It in the Sky or Online

Image: Supermoon over St. Petersburg

The full moon is seen rising in the sky above the domes of the Smolny Cathedral in St. Petersburg, Russia, on Monday evening. Monday night's full moon, also known as a Harvest Moon, is the third and final "supermoon" of 2014. The phenomenon, which scientists call a "perigee moon," occurs when the full moon is closer to Earth than average and appears larger and brighter than the typical full moon. Dmitry Lovetsky / AP

Say farewell to summer — and to this year's series of "supermoons" — by looking for Monday night's bigger-than-usual full moon in the sky, or on a display screen near you.

This is considered a supermoon because the full phase occurs at 9:38 p.m. ET, not long after the moon passes at the closest point in its orbit around Earth. That makes it several percentage points bigger and brighter than the average full moon. A similar situation was in effect for the full moons of July and August. In fact, last month's supermoon was the most super of the year's full moons.

What Is a Supermoon? 0:41

Monday's full moon, however has an extra claim to fame. It's known as a "Harvest Moon" because of its status as the full moon closest to the Northern Hemisphere's autumnal equinox on Sept. 22. The tradition is that the bright moon helps light the way for farmers bringing in their crops late into the evening — and if moonlight really does make any difference, the harvesters just might appreciate this year's super glow.

Bob Berman, an astronomer associated with the Slooh virtual observatory, says the Harvest Moon ranks as the year's most famous full moon. "Yet it's bathed in myth and misconception, even without all the extra 'supermoon' business," he said in a statement.

Berman and Slooh host Geoff Fox will delve into the myths and the marvels surrounding the Harvest Supermoon during a webcast starting at 9:30 p.m. ET Monday. There'll be live video views from locations around North America, and from Slooh's robo-telescope in the Canary Islands. The show can be seen via Slooh's website or LiveStream. Viewers can ask questions during the show by using the Twitter hashtag #SloohSupermoon.

Image: Supermoon vs. Mini-moon
This graphic compares the size of the moon when it's closest to Earth, during a supermoon full phase (left), with how a full moon would look when it's farthest from Earth (right). The Weather Channel

Even though supermoons aren't all that much bigger than run-of-the-mill full moons, the occasion provides a great excuse for making a to-do over moongazing.

If the weather's clear, there are two strategies for supermoon-watching. One is to wait until midnight, when your viewing location is at its minimum distance from the moon. The other is to catch sight of the moon just after it clears the eastern horizon, when the "moon illusion" effect is at its peak. This online calculator from TimeandDate.com tells you when moonrise occurs in your area, and the Clear Sky Chart shows the forecasts for sky conditions.

For centuries, experts have debated why the moon looks bigger when it's low in the sky. Some say it's because our brains are wired to compare the size of the moon with faraway objects on the horizon. Others say it has to do with the way we perceive clouds as they move from the horizon to directly overhead. Either way, a low-slung moon with terrestrial objects in the foreground makes for a prettier picture.

Pictures can be the best part of the supermoon experience. If you snap a super snapshot of the supermoon, please share it with us: Just use the hashtag #NBCSupermoon on Twitter or Instagram, or pass it along using NBC News' FirstPerson photo-upload website. We'll share a selection of the best supermoon shots in a future posting.

For still more supermoon views, check out the pictures that are already being posted to SpaceWeather.com's image gallery.