Retired NASA eclipse scientist Fred Espenak has been watching the night sky since he was eight and plans to look again at the upcoming lunar eclipse on Sunday (May 15).
After staring at the sky for about six decades, the Arizona native said he still enjoys watching the shadow shift as the moon turns red during a total lunar eclipse and goes completely into Earth’s deep shadow. Read our full guide to the Super Flower Blood Moon lunar eclipse to get ready for the epic lunar event.
Webcasts: How to Watch Super Flower Blood Moon Lunar Eclipse Online
“If you look at it 10 seconds before or 10 seconds after, you can’t tell the difference,” Espenak told Space.com about lunar eclipses. “It’s more of a gradual effect. You see changes from minute to minute, but not from second to second.”
The Flower Moon eclipse will be visible in total phase from parts of the Americas, Antarctica, Europe, Africa and the eastern Pacific Ocean. This eclipse will feature a moon that appears somewhat large, on the verge of supermoon status. If you’re hoping to photograph the moon, or get your gear ready for the total lunar eclipse, check out our best astrophotography cameras and best astrophotography lenses. Read our guides on photographing a lunar eclipse and photographing the moon with a camera for some helpful tips for planning your lunar photo shoot.
Not everyone agrees that the full Flower Moon is a supermoon due to different definitions. Espenak’s definition is based on the very first supermoon, when astrologer Richard Nolle defined it in 1979 as a full moon that comes to Earth within 90% of its closest point in orbit.
“That’s the definition I use, because that was the first. It sets a precedent for me,” he said. “But first of all, that 90% is purely arbitrary. There’s no real justification for why it should be 90%, or 89 or 91.”
But Espenak calculates supermoons to also account for changes in the moon’s orbit during each lunar cycle, including the perigee (nearest point) and apogee (farthest point). NASA, which follows the strict 90% definition, says the Flower Moon isn’t a supermoon, but June’s full moon will be.
Espenak’s rationale comes down to lunar variability. “The perigee point and the apogee point of each individual [moon] orbit varies from orbit to orbit,” he said. That’s because the gravitational pull of the Earth and the sun pulls on the moon across its orbits.
“The limits of what you get as a supermoon varies from orbit to orbit,” he added. “So to determine whether a particular moon is a supermoon or not, you have to look at the moon’s specific orbit during that lunar cycle.” (A lunation is a lunar month, or the time that elapses between new moons.)
Epsenak’s definition of supermoon lists the following four full moons as supermoons: May 16, June 14, July 13, and August 12. But he noted that streak isn’t particularly uncommon. According to its website, 2023 will also see four consecutive full supermoons, just like 2024. Even 2025 will have three in a row.
“Every 14 months or so, you get a series of moons that are past that 90% threshold. So very often, every 14 months or so, we’re going to get two or more, probably three to four,” he explained. He added that the relative size of the larger full moon, however, is so small that even it cannot easily tell the difference just by looking at the sky.
While the supermoon’s size will be subtle, the eclipse will get quite interesting once it makes first umbral contact with the moon. The penumbral or lighter eclipse introduces subtle shadows, but the umbra, Espenak said, will “look like the Cookie Monster took a piece” from the moon.
“You don’t really see the color until you get close to the totality,” he said. The Blood Moon, he added, should be very easy to spot within minutes of totality, although that will depend on the lighting and atmospheric conditions in your area.
“In dark locations, it’s easier to detect subtle colors and features,” he said. “Early-eyed observers will find that the part of the moon that is deeply in the shadows will be able to see some color in it in the last five to 10 minutes of the partial phases as we approach totality.”
However, the Blood Moon may not look completely red. “That ranges from bright orange, to fire truck red, to a dark brownish color, to almost invisible dark brown gray,” Espenak said. “But most of the time it’s orange to red, and that’s because of the colors caused by the sunlight filtering through Earth’s atmosphere.”
While the timing will depend on your location, TimeandDate.com says the partial eclipse phase of the lunar eclipse will begin on May 15 at 10:28 PM EDT (0228 GMT on May 16). It will reach the red-colored Blood Moon peak on May 16 at 12:11 PM EDT (0411 GMT). The event ends at 1:55 AM EDT (0555 GMT). Note that the penumbral eclipse begins about an hour earlier and ends about an hour after the partial eclipse.
Editor’s Note: If you take a great photo of a lunar eclipse (or your own eclipse webcast) and want to share it with Space.com readers, please send your photo(s), comments, and your name and location to [email protected]