A blood moon is a total lunar eclipse, when the full moon sits entirely inside Earth’s dark shadow and glows red, orange or coppery brown instead of disappearing. The red phase, called totality, lasts from a few minutes to about 1 hour 46 minutes.
Key facts
- A blood moon is the popular name for a total lunar eclipse.
- The red color is sunlight filtered and bent by Earth's atmosphere, the light of all the world's sunrises and sunsets.
- Dust and volcanic aerosols can make a blood moon much darker; astronomers rate it on the 0–4 Danjon scale.
- The term spread widely during the four total lunar eclipses of 2014–2015.
Why does the Moon turn red during a total lunar eclipse?
The Moon turns red because Earth’s atmosphere bends sunlight into Earth’s shadow and filters out most of the blue light on the way.
During totality, Earth blocks all direct sunlight from reaching the Moon. A thin ring of atmosphere still surrounds the planet, though. Sunlight passing through that ring is refracted, or bent, inward toward the shadow. On the way, air molecules scatter blue light much more strongly than red light, an effect called Rayleigh scattering.
Rayleigh scattering is also why the daytime sky is blue and sunsets are red. NASA describes the result during an eclipse as if all the world’s sunrises and sunsets were projected onto the Moon. The reddened light is faint, so the Moon looks dim and colored rather than bright.
Only a total eclipse produces the full effect. A blood moon is one of three types of lunar eclipse, and in the penumbral and partial types the bright, uneclipsed part of the Moon drowns out the red glow.
When is the next blood moon?
The next blood moon is the total lunar eclipse of , visible at least in part from Europe, Africa, the Middle East, Asia, Australia, New Zealand and the Pacific. It is the first eclipse marked “total” in the table below; the penumbral and partial eclipses in the list do not turn the whole Moon red.
2027 has no total lunar eclipse at all, only three penumbral ones, so the wait after the blood moon of March 3, 2026 is unusually long. The totality column shows how long each blood moon stays red. The “where visible” column shows which regions have the Moon above the horizon.
Every blood moon falls on a full moon, and our list of the next full moon dates flags any full moon that brings an eclipse.
Why are some blood moons brighter or darker than others?
A blood moon’s brightness depends on how deep the Moon goes into Earth’s shadow and on how clean, cloudy or dusty Earth’s atmosphere is at the time.
The umbra is darkest at its center. A Moon that passes close to the center looks darker and deeper red. A Moon that passes near the edge of the umbra often shows a brighter, orange or yellowish rim on one side.
Earth’s atmosphere matters even more. Water vapor, dust and volcanic ash all filter the light that reaches the Moon. NASA notes that large volcanic eruptions are often followed by very dark, red eclipses for several years. Thick cloud along the edge of Earth, as seen from the Moon, also dims the glow.
Astronomers rate the result on the Danjon scale, named after the French astronomer André Danjon:
| Danjon value | Appearance at mid-totality |
|---|---|
| L = 0 | Very dark; Moon almost invisible |
| L = 1 | Dark gray or brownish; details hard to make out |
| L = 2 | Deep red or rust; very dark center, brighter outer edge |
| L = 3 | Brick red; bright or yellow rim on the shadow |
| L = 4 | Very bright copper-red or orange; bluish, very bright rim |
Where does the term “blood moon” come from?
The image of a Moon “turned to blood” is ancient, but the term’s wide modern use dates from 2013–2015, when two pastors linked four total lunar eclipses to biblical prophecy.
Older sources describe the same sight. The Book of Joel says the Moon will be turned “into blood.” The Anglo-Saxon Chronicle reported in 734 CE that the Moon looked “as if it had been sprinkled with blood.”
The modern use comes from the lunar tetrad of 2014–2015. A tetrad is a series of four total lunar eclipses about six months apart, with no partial eclipses between them. Those four eclipses fell on April 15, 2014, October 8, 2014, April 4, 2015 and September 28, 2015 (UTC).
Christian pastors Mark Biltz and John Hagee called them “blood moons,” and Hagee’s 2013 book Four Blood Moons made the phrase widely known. News outlets now use “blood moon” for any total lunar eclipse.
Folklore uses the name in one more way. The Hunter’s Moon, the autumn full moon after the Harvest Moon, is sometimes called a Blood Moon, because it often rises reddish near the horizon. That use has nothing to do with eclipses.
What is a super blood moon?
A super blood moon is a total lunar eclipse that falls on a supermoon, a full moon close to perigee, so the red Moon looks slightly larger than usual.
This site counts a full moon as a supermoon when it lies within 90% of perigee for that orbit. A full moon at perigee can look up to about 14% larger than one at apogee. A Moon near perigee also moves faster along its orbit, so super blood moons tend to have shorter totality.
Recent examples include:
- January 31, 2018: a super blood moon that was also a Blue Moon, the second full moon of that January.
- January 21, 2019: a super blood moon on January’s Wolf Moon.
- May 26, 2021: a super blood moon with totality of only about 15 minutes.
Is it safe to watch a blood moon?
Yes, a blood moon is completely safe to watch with the naked eye, binoculars or a telescope, because the Moon is in shadow and no direct sunlight reaches your eyes.
Binoculars bring out the color and the shading across the disc. A total solar eclipse is the opposite case: its partial phases require certified eye protection. The lunar vs solar eclipse comparison explains why the two events need such different care.
What did ancient cultures believe about the blood moon?
Many cultures explained the darkened, reddened Moon as an attack on the Moon or a warning, according to National Geographic’s survey of eclipse myths.
- Inca: a jaguar attacked and ate the Moon, which explained its blood-red color. People feared the jaguar would then come down to Earth and attack people.
- Mesopotamia: seven demons assaulted the Moon. Because the king stood for the land, people saw the eclipse as an attack on the ruler and installed a substitute king to take the harm.
- Hupa (Native American): the Moon’s pets, mountain lions and snakes, attacked him when they were not fed, making him bleed. His wives protected and healed him, ending the eclipse.
- Luiseño (Native American): an eclipse meant the Moon was ill, and people sang chants or prayers to help it recover.
- Batammaliba (Togo and Benin): the Sun and the Moon were fighting, and people encouraged them to stop. The eclipse became a time to settle old quarrels.
Modern astronomy has turned the blood moon into one of the most predictable sights in the sky. NASA’s eclipse catalogs give the date, time and length of every total lunar eclipse across thousands of years.