Replete with a full-on satanic ritual conducted under the red light of a blood moon eclipse, Netflix’s The Chilling Adventures of Sabrina is a far cry from the happy-go-lucky original. But as chilling as that blood moon scene is, astronomy experts tell Inverse that there’s no reason to fear the woods at midnight this Halloween. They do, however, point out that a moon with eerily similar features is in our near future.

Caution: Mild spoilers for Sabrina ahead.

In the first episode, Aunt Zelda explains that the blood moon eclipse necessary for the dark baptism only occurs every 66 years. This number is probably fictional, explains Andrew Shaner, who leads the lunar education efforts at the Lunar and Planetary Institute in Houston. A blood moon is simply the result of a lunar eclipse positioned in a certain way, and lunar eclipses happen fairly regularly. In the 21st century, we’re going to experience 221 of them, according to NASA.

Previously, Inverse explained what a blood moon is:

A blood moon is simply the result of a Supermoon — where a full moon or new moon occurs as the little rock makes its approach to the Earth — and a total lunar eclipse — when the sun, Earth, and moon are aligned and cause the Earth to cast a shadow on the moon — happening at the same time. It’s actually called a Supermoon Lunar Eclipse.

So, while blood moon eclipses are not that rare, Aunt Zelda is right to think that a lunar eclipse that has that bright shade of red and occurs at the right time for a Dark Baptism is incredibly rare, Shaner tells Inverse. But fortunately for Auntie Z and other witches, there’s a wealth of alternative options for equally spooky moons, and one of them is coming soon.

lunar eclipse blood moon Sabrina
A 2015 lunar eclipse 

What Makes the Moon So Bloody

Usually, Shaner says, a lunar eclipse happens about twice per year, when the Earth is positioned directly between the sun and the moon. When this happens, the moon is completely obscured by the earth’s “umbral shadow,” the giant cone-like silhouette cast by the Earth as the sun hits it from one side. When this happens, some of the light from the sun is absorbed by the Earth’s atmosphere. Red light, however, isn’t absorbed, and so it bounces off the moon, giving it a blood-like tinge.

But the brilliant red we see in during Sabrina’s dark baptism is quite rare for an eclipse, admits Shaner. For the moon to actually get that red, it has to be positioned in one particular place in the earth’s shadow.

“It depends on how much of the moon will pass through the earth’s shadow. That will change how much the moon changes color,” Shaner says.” n some eclipses, it barely passes through the shadow, so it just becomes a darker gray color, versus when it really comes right through the middle of the shadow you get this dark red color.”

For the blood moon to get that red, it would have to pass through the exact center of the earth’s shadow, which is called the umbra.

red blood moon
The closer the earth gets to the center of the cone shaped umbral shadow, the brighter its red color will become

Shaner says to think about it like putting a piece of paper horizontally through the earth. The closer the moon gets to that center, the darker the red color will be and, importantly, the longer the eclipse will actually last. This is what we see in Sabrina: a moon that has perfectly aligned with that central mark, resulting in a brilliant, lengthy eclipse.

Upcoming Dates

This past July, we experienced the longest eclipse of this century. During that eclipse, the moon passed through the sweet central spot in the umbra that Shaner described. Unfortunately, it occurred at 3:41pm EST, so it would have been of no use to the witches of Greendale, which according to fan theory is likely near Riverdale in New York State. After all, for a lunar eclipse to be appropriate for a Dark Baptism, it would have to happen at night.

Fortunately, as astronomer Jana Grcevitch, Ph.D., at Columbia University’s astronomy department tells Inverse, there are some options in our future. “Is it theoretically possible there is a total lunar eclipse visible at midnight from a town in upstate NY? The answer here is yes!” Grcevitch says.

On October 29th 2050, there will be a visible lunar eclipse, so that’s one possibility. But if Halloween isn’t a requirement for a Dark Baptism, there also one happening on January 21st 2019 at 12:12 am EST.

Depending on how crucial the Halloween date is, there are plenty of opportunities for Sabrina to re-do her dark baptism.

Photos via Wikimedia Commons (1, 2, 3)