This weekend’s full moon will likely draw your eye even more than a regular one does.
Newsweek reports that what’s known as the full hunter’s moon—the first full moon after the harvest moon—will rise right around sunset, making it seem both much larger and more orange than usual. Though you’ll likely be able to spot it from Saturday, October 12 through the early morning hours of Tuesday, October 15, the best time to look up is Sunday night, October 13, when the moon reaches peak fullness.
According to The Old Farmer’s Almanac, the hunter’s moon may seem so huge because of a simple trick our eyes play on us called the “moon illusion.” Usually, when the moon is high and far from the horizon, it’s the main thing we see in the sky. Because the sky itself is so unfathomably vast, the moon looks pretty small. The hunter’s moon, however, appears lower in the sky, giving us a chance to view it next to things like trees and buildings. Since the moon is so much larger than those objects, our brains may process it with a better sense of scale.
The reason the hunter’s moon often glows orange is also related to its lower position. The moon is actually closer to us when it’s higher in the sky, so the light it reflects has to travel a shorter distance to reach our eyes, leaving the shorter wavelengths of blue light intact. When the moon is low, the air scatters those short blue wavelengths before they get to us, and only the longer, reddish wavelengths make it through.
Though we don’t know for sure why it’s called a hunter’s moon, The Old Farmer’s Almanac suggests that it may have once indicated the beginning of prime hunting season, when hunters could easily spot animals in fields that harvesters had just cleared after the previous month’s harvest moon.
And, after the hunter’s moon has come and gone, be sure to catch the full beaver moon in November.