Astronomy Essentials

The full Hunter’s Moon is October 20, 2021

Hunter's Moon over temple with candles around every floor and onion dome on top.
The West’s Hunter’s Moon is sometimes celebrated as Kartik Purnima in India. In 2021, the dates vary a bit. The festival will come around the November full moon (night of November 18-19 in India). Swami Krishnananda in Ranchi, India, captured this photo during Kartik in 2017. Thank you, Swami Krishnananda!

Hunter’s Moon October 20, 2021

In western skylore, the Hunter’s Moon is name for the full moon following the Harvest Moon. It’s usually in October, but in some years falls in early November. In 2021, the full Hunter’s Moon will rise on October 20 for most of the world. Eastern Australia and New Zealand will see the full moon on October 21. The Hunter’s Moon will be 100-percent lit on October 20 at 14:56 UTC; translate UTC to your time. For North America, the moment of full moon is 10:56 am EDT or 7:56 am PDT on October 20. So, if you’re up before sunrise on Wednesday morning, October 20, the full Hunter’s Moon will be setting. On both the evening of October 19 and 20, the moon will be more than 99-percent lit as it ascends in the east.

Every full moon has a slew of nicknames, and most are tied to months of the year. However, some moon names, such as the Harvest and Hunter’s Moons, are tied to seasons. The Harvest Moon is the full moon closest to the autumnal equinox. With the autumnal equinox in the Northern Hemisphere occurring on September 22 or 23, that puts most Harvest Moons in the month of September. But every three years the Harvest Moon is in early October. In North America, the Harvest Moon was a time when the bright moon meant farmers could stay out later, working in their fields, gathering in the crops before the first freeze. When the harvest was over, the farmers would turn to hunting deer and other animals to bolster their food stores before winter; thus, the Hunter’s Moon.

Giant pink moon over many-windowed flat roof building with autumn trees in foreground.
2017’s Hunter Moon – November 3 – over Bloomington, Indiana, via Ken Meadows.

What makes a Hunter’s Moon special?

Nature is particularly cooperative around the time of the autumn equinox to make the fall full moonrises unique. On average, the moon rises about 50 minutes later each day. But when a full moon happens close to the autumnal equinox – either a Harvest or a Hunter’s Moon – the moon (at mid-temperate latitudes) rises only about 30 to 35 minutes later daily for several days before and after the full moon. The reason is that the ecliptic – or the moon’s orbital path – makes a narrow angle with the evening horizon around the time of the autumn equinox.

The result is that there’s a shorter-than-usual lag time between successive moonrises around the full Hunter’s Moon.

Early evening moonrises make every Hunter’s Moon special. Every full moon rises around sunset. After the full Hunter’s Moon, you’ll see the moon ascending in the east relatively soon after sunset for a few days in a row at northerly latitudes.

If you’re in the Northern Hemisphere, look for the moon to be bright and full-looking for several nights from around October 18 to the 21. Around all of these nights, you’ll see a bright round moon in your sky, rising around the time of sunset, highest in the middle of the night.

Diagram of sky's dome with slanted line of ecliptic across it.
Here in the Northern Hemisphere, it’s autumn now. That means the ecliptic – or sun and moon’s path – makes its narrowest angle with your horizon in early evening. Image via ClassicalAstronomy.com.
Diagram of horizon with moon's position above and below it along shallow ecliptic.
When the angle of the ecliptic is narrow, the moon rises noticeably farther north on your horizon from one night to the next. So there’s no long period of darkness between sunset and moonrise. In other words, around the time of an autumn full moon, many people see the rising moon ascending in the eastern sky in twilight, for several evenings in a row. If you’re in the Southern Hemisphere, your evening ecliptic is nearly perpendicular to your early evening horizon now. You’ll see the full moon rise in twilight, but the next night’s moon come up in darkness, much later at night.  Image via ClassicalAstronomy.com.

Find the time of moonrise in your location

My favorite source of moonrise times is the Custom Sunrise Sunset Calendar. Once you get to that page, be sure to click the box for “moon phases” and “moonrise and moonset times.”

Distant lightning bolt from cloudy sky above silvery ocean.
Light from a hidden Hunter’s Moon lights the ocean’s surface – October 23, 2018 – from Michael Busch in Long Island, New York.

Is a Hunter’s Moon bigger or brighter?

No. The Hunter’s Moon is just an ordinary full moon with a special path across our sky. Still, many of us do think the Hunter’s Moon looks bigger … or brighter … and more orange than usual. Why?

It’s because the Hunter’s Moon has a powerful mystique. Many people look for it shortly after sunset around the time of full moon. After sunset around any full moon, the moon will always be near the horizon … because full moons rise at sunset. It’s the location of the moon near the horizon that causes the Hunter’s Moon – or any full moon – to look big and orange in color.

Orange moon near the horizon. The orange color of a moon near the horizon is a true physical effect. It stems from the fact that, when you look toward the horizon, you’re looking through a greater thickness of Earth’s atmosphere than when you gaze up and overhead. The atmosphere scatters blue light – that’s why the sky looks blue. The greater thickness of atmosphere in the direction of a horizon scatters blue light most effectively, but it lets red light pass through to your eyes. So a full moon near the horizon – any full moon near the horizon – takes on a yellow or orange or reddish hue.

Big moon near the horizon. The bigger-than-usual size of a moon seen near the horizon is something else entirely. It’s a trick that your eyes are playing – an illusion – called the Moon Illusion.

Ascending line of full moons above multiple overlapping crescent-shaped roofs of large structure.
Rising Hunter’s Moon. Photo by Abhinav Singhai, 2014.

How did the Hunter’s Moon get its name?

There are many stories surrounding the names of the moons, including the Hunter’s Moon. From a practical standpoint, the Harvest Moon and subsequent Hunter’s Moon provided light in the evenings for farmers and hunters to finish their tasks.

In autumn, the full Harvest Moon and the nearly full moons on the evenings before and after all rise very close to sunset. The sky transitions from sunlight to moonlight without much darkness, so farmers can keep working straight into the evening. A month later, after the harvest ended, the full Hunter’s Moon illuminated prey, scooting along in the stubble left behind in the fields.

Who named the Harvest and Hunter’s Moon? Those names probably sprang to the lips of farmers and hunters throughout the world, on autumn evenings, at times of the full moon.

Person standing silhouetted against sea inlet with moon rising over horizon.
Full Hunter’s Moon rising over the Bothnian Sea, Sweden, on November 4, 2017, via Jörgen Norrland Andersson.

A note to those in the Southern Hemisphere

If you’re in the Southern Hemisphere, your Harvest and Hunter’s Moons center on the March equinox, your autumn equinox. Much of what we say in his post – the general information about Harvest and Hunter’s Moons – applies to you, too… next March and April. Right now, your full moon will be doing the opposite of a Hunter’s Moon. That is, for the Southern Hemisphere around the time of the September and October full moons, there’s a longer-than-usual time between moonrises on successive nights.

Bottom line: You can find the date and time of the Northern Hemisphere’s full Hunter’s Moon for October 2021, and then learn why this annual moon brightens the evening for a string of days.

Posted 
October 19, 2021
 in 
Astronomy Essentials

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