By this point in the year, you’ve usually already missed your chance to see the Harvest Moon. This year, however, it’s a little later than usual. It pushes right into October—perfect for the Halloween season!
The “Harvest Moon” is the name given to the full moon that falls nearest to the autumnal equinox (the first day of fall), which took place Sept. 22. Usually, this Harvest Moon occurs before the autumnal equinox—which is why it is oftentimes also called the September Moon. But this year, it won’t be until Oct. 5, a few weeks later than usual.
About every three years, the October full moon actually rises closer to start of fall, making that one the Harvest Moon instead. This year, September’s full moon rose on Sept. 6. Counting by calendar days, this means the full moon on Oct. 5 is closer to the autumnal equinox than the September moon. Pretty fascinating!
The moon served as a timekeeper for ancient civilizations, with different cultures assigning unique names to the full moons based on the time of year they occur. The Harvest Moon provides the most light at the time when it’s needed most—to complete the harvest. Other full moon names include the full snow moon, full flower moon and the full cold moon, signaling winter cold and when the nights become long and dark.
Harvest Moon’s special qualities
Besides its timing, what else makes the Harvest Moon so special? Well, according EarthSky, a few factors make this full moon standout from the typical one.
First, during this time of year, the moon rises about 50 minutes later each day. However, when a full moon happens near the autumnal equinox, it rises only about 30 to 35 minutes later each day for a short period of time. Why? The moon’s orbit creates a narrow angle with the evening horizons.
So, what does this all mean?
That 10 to 15 extra minutes makes a big difference in when we see the moon come up over the horizon. During the days surrounding the full Harvest Moon, it will rise either during or close to twilight. As a result, to us, the moon will look full for a few nights in a row. In reality, though, it hits 100 percent fullness at2:40 p.m. Eastern Daylight Time,
You can see it rise at 6:51 p.m. EDT on Oct. 5 and set at 7:40 a.m. EDT on Oct. 6.
Why does the full Harvest Moon appear orange?
Also, because if the Harvest Moon’s rising time and location, it typically appears more orange than usual. This happens due how we see the moon at the horizon. When we look at the horizon, we look through a larger thickness of the Earth’s atmosphere. And, since the atmosphere scatters blue light, our eyes can see more red light. Therefore, when we see the moon, we notice the shades of red, orange and orange.
Is the Harvest Moon larger than usual?
Ever notice how sometimes the moon looks bigger some times than others? During Harvest Moon season, people may wonder if a special quality makes it bigger than usual. It turns out the moon never actually changes size. However, our eyes fall for the moon illusion.
The moon illusion is when our eyes and brain get tricked into thinking the moon looks unusually large. In fact, the moon looks larger when we see it close the horizon compared to higher in the sky. This happens because other objects near the horizon look smaller than the moon. Think about it this way, when you see trees or buildings near the horizon as the moon rises, the moon looks huge. However, when the moon rises higher in the sky, it looks smaller in comparison. That’s because it only has the big sky around it and no other objects to provide size perspective.
Get out and enjoy the full Harvest Moon
Sure, you probably don’t have crops to tend to, but the rare full moon offers other great reasons to get out there and take advantage of its brightness. It provides the perfect opportunity for a fall nighttime walk. Or you can pull out the telescope, since many of the features on the surface of the moon are visible!
The Harvest Moon will be back to its normally scheduled September glow on Sept. 24, 2018.