A Field Guide to Full Moons

From supermoons and blood moons to black moons and blue moons, here’s a cheat sheet to the full moon in all of her luminous guises.

Public Domain. The Harmonia Macrocosmica of Andreas Cellarius

It appears we have entered an era of moon near-hysteria, with each month bringing about a rush of excited stories detailing the unique charms of whatever full moon is in the works at the time. And while some fatigued journalists will kvetch about the hype “it’s just a full moon, for heaven’s sake” I think it’s great. How wonderful that people are excited to go outside, look up to the heavens, and marvel at the beauty of the sky.

That said, it does get confusing what with this moon and that moon; the supermoons and strawberry moons and black moons and you name it. Case in point, the second full moon of January 2018 was a “super blue blood moon.” What in the world does that mean?

To make sense of all the lunacy, we present some basic definitions of the various full moons.

Black Moon

The black sheep of the moon family, a black moon may not be that much to look at, since it’s the second new moon within a month – and since we can’t see new moons, well we’ll just have to appreciate that it’s there. (And while, yes, a new moon isn't exactly a full moon, per se, it is full on the other side.) Think of it as the esoteric twin of the exuberant blue moon; see below.

Blood Moon

This one comes with a pretty simple description. A Blood Moon occurs during a lunar eclipse. NASA explains, “while the Moon is in the Earth’s shadow it will take on a reddish tint, known as a ‘blood moon.’” But we can make it a little more confusing by noting that in Native American tradition, the October full moon was referred to as the Full Blood Moon by some Indigenous People (see Strawberry Moon, below, for more).

Blue Moon

A blue moon occurs when a single month hosts two full moons. The lunar calendar almost lines up with our monthly calendar, but not exactly. The lunar cycle – the time from one new moon to the next – is on average 29.53 days. Usually this means we get one full moon and one new moon each calendar month. But given that our months are generally longer than 29.53 days, it means that once in a blue moon ... we get a blue moon. (Which is about once every 2.7 years.)

Strawberry Moon

While we have our months to help us keep track of the schedule, early Native American nations kept tabs on time by observing the seasons and employing the celestial clock known as the moon. They marked the passing of the year in full moons, each one named for a predominant component of the season. Every full moon had a name, and while they varied from nation to nation, June’s Full Strawberry Moon was universal amongst all of them.


Supermoons occur when a full moon happens during perigee, the point in its orbit when it’s closest to Earth – the result can make the moon appear up to 14 percent larger and 30 percent brighter than other full moons. Add in a little "moon illusion" and the appearance is, in a word, super! .

Harvest Moon

The Harvest Moon is the full moon closest in date to the autumnal equinox; it is usually the September full moon that takes the title of Harvest Moon. But if the October full moon is closer to the date of the equinox, she takes the name. .

Hunter’s Moon

The Hunter’s Moon is the full moon following the Harvest Moon; which means that it is usually in October, except for when the Harvest Moon occurs in October – then, the Hunter’s Moon happens in November.

So there you have it; now when you see something like a super blue blood moon in the news, you can know that it's simply the second full moon of the month that happens to be occuring during perigee at the time of a lunar eclipse! For more, here's a great crash course in all things moon by PBS.

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