Eyes to the sky this weekend for the Harvest Moon

The last Full Moon of summer will shine in the night sky.

Check your local weather forecast for clear skies. The Harvest Moon is rising and you won't want to miss it!

There are some great skywatching opportunities this weekend. Saturn, Jupiter, and Mars continue to shine in the sky throughout the night, with Venus joining them in the hour or so before dawn.

Along with these bright planets, the Moon will light up the nights, appearing full from Thursday evening to Sunday morning, but reaching its Full Moon phase early Saturday morning.

Corn Moon...

For nearly a century, the various Farmers' Almanacs have printed a list of names for each Full Moon of the year. This list is derived from the names used by various First Nations peoples, as well as from Colonial and European folklore.

According to The Old Farmer's Almanac, the September Full Moon is usually called the Corn Moon.

"This time of year — late summer into early fall — corresponds with the time of harvesting corn in much of the northern United States," the almanac says. "For this reason, a number of Native American peoples traditionally used some variation of the name 'Corn Moon' to refer to the Moon of either August or September."

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Other names for this Full Moon include the Autumn Moon, Drying Grass Moon, Falling Leaves Moon, Yellow Leaf Moon, and even Ice Moon, depending on which folklore you follow.

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This graphic collects all the relevant data about each Full Moon of 2022, including their popular names, whether they are a 'super' or 'micro' Moon, a 'perigee' or 'apogee' Full Moon, and whether they are remarkable in some other way (Harvest Moon, or due to a lunar eclipse). Credit: Scott Sutherland/NASA's Scientific Visualization Studio/Fred Espenak

Other cultures assign names to Full Moons as well.

In Japan, this weekend is Tsukimi (which translates as "moon-viewing"), a festival to honour the autumn Moon and show gratitude for the harvest. In China, they will be celebrating Zhong Qui Jie, the mid-autumn festival, while in Korea they have a similar holiday known as Chuseok.

According to the Hindu calendar, this Full Moon is the beginning of Pitru Paksha, a time of the year to honour one's ancestors.

NASA has names for this Full Moon, as well. They call it the GRAIL Moon and the LADEE Moon, after two lunar satellite missions that launched in September — Gravity Recovery and Interior Laboratory (GRAIL) in 2011 and Lunar Atmosphere and Dust Environment Explorer (LADEEE) in 2013.

...and the Harvest Moon??

The September Full Moon has one other name.

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Each time the Autumnal Equinox rolls around, the Full Moon that occurs closest to that date is called the Harvest Moon.

There are times when the Harvest Moon is in October. We saw this in 2020, when the Harvest Moon fell on October 1, and was followed by the Halloween Hunter's Blue Micro Moon.

In 2022, there are Full Moons occurring on Sep. 10 and Oct. 9, and the Equinox is on Sep 23. So, this year, like most, the September Full Moon is the Harvest Moon.

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The Harvest Moon. Credit: Jeff Taylor/UGC

According to NASA, "The first known written use of this name in the English language (per the Oxford English Dictionary) was in 1706. On average moonrise is about 50 minutes later each night. Around the Harvest Moon, this time is shorter, about 25 minutes for the latitude of Washington, D.C., and only 10 to 20 minutes farther north in Canada and Europe. During the fall harvest season farmers sometimes need to work late into the night by moonlight (especially before the introduction of artificial lights)."

WATCH: See the Moon, hour by hour for all of 2022, in less than 5 minutes

The Mesmerizing Moon Illusion

You step outside just after sunset, and there, looming above the horizon is a Full Moon that looks absolutely enormous! You snap a picture or two with your cell phone, and something doesn't quite look right... the Moon actually looks smaller on the phone's screen. Later, around midnight, you spot the Moon again, high above your head, and it definitely looks smaller than it did earlier.

So, what's going on?

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This is not something the Moon, itself, is doing. In fact, for an observer on Earth's surface, watching at moonrise, the Moon is actually more than 6,400 km farther away from them compared to when it's directly overhead at midnight.

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This graphic shows the distance between an observer on Earth's surface at moonrise vs midnight. Credit: Scott Sutherland/NASA's Goddard Space Flight Center

Instead, the apparent change in size of the Moon between when it rises and when it's overhead is due to a trick of our mind known as The Moon Illusion.

There are times when the Moon actually does look bigger, such as during a supermoon, when the Moon is physically thousands of kilometres closer to Earth than usual. Other times, though, we just think the Moon looks larger.

As our eyes take in the world around us, our brain knows from experience that objects close to us tend to appear larger and in focus. In contrast, distant objects tend to be tiny and blurry. From this, it also knows that for a distant object to appear in focus, it must be very large.

ugc calgary full moon

This close-up of the Harvest Moon was snapped in Calgary, AB, on September 13, 2019. Credit: Siv Heang

So, when we see a bright Full Moon hanging crisp and clear in the sky above the horizon, it is contrasted by all of the objects on the ground, which appear smaller and blurrier the closer they are to the horizon. This combination confuses the brain.

So, to compensate, the brain interprets the Full Moon as being much bigger than it truly is. To be clear, the Moon is certainly much larger than any of the objects on the horizon (it's 3,474 km across), but this 'illusion' gives us the impression that the Moon looks enormous!

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This zoomed-in image of the Full Moon was captured from Salisbury, NB, on February 9, 2020, and uploaded into the Weather Network's UGC gallery. Credit: Darlene MacLeod/Smith

Look again when the Moon is high above our heads and it will seem smaller. Since there's nothing right next to it in our field of view for our brain to compare it with, we see it's 'true' size.

We have a few tricks of our own that can cancel out the Moon illusion, though.

For the first one, we don't need technology. Just go outside after sunset and find the Moon near the horizon. Stretch your arm towards it, and cover the Moon with your thumb or even your pinky finger. Note how big the Moon looks compared to the digit in question, and keep that in mind. Maybe even take a picture of it, if you want. Later in the night, check out the Moon again when it is high in the sky. It may appear smaller than when you saw it earlier, but repeat the step to cover it with your thumb or finger. Compare it with what you saw before, and you'll find that the Moon is actually precisely the same size at both times.

There is a way technology can help us, though. When the Moon is low on the horizon, take out your cell phone, turn your camera on, and point it at the Moon.

Note: it is possible for the Moon illusion to still work on us when looking at a picture or video. This is because the brain will make the same judgments of distance, blurriness, and size as it did when looking at a 'live' scene.

Still, directly comparing what we see in the sky at that time to what is shown on our small cell phone screen can help put things into better perspective. Plus, you can also take a few pictures to upload into the Weather Network UGC Gallery while you're at it!