Blood Moon & Lunar Eclipse Explained
A blood moon is the red or copper-colored Moon seen during a total lunar eclipse. The color appears when Earth blocks direct sunlight and its atmosphere bends some red and orange light into the shadow.
Blood moon is a popular name rather than a formal astronomical term. Some sources also use it for a very deep partial eclipse, but we use the name for total lunar eclipses.
When is the next blood moon?
The next blood moon reaches maximum eclipse on December 31 at 11:51 a.m. EST, or December 31 at 8:51 a.m. PST. Totality runs from 11:15 a.m.–12:28 p.m. EST, or 8:15 a.m.–9:28 a.m. PST.
The fact sheet above shows whether any part of the eclipse will be visible from your location. Note: eclipse visibility is local—the event may unfold high in the sky in one region while the Moon is below the horizon somewhere else.
If the Moon is already fully eclipsed when it rises, or sets before that phase ends, you may see only part of the event.
Upcoming blood moons and lunar eclipses
What happens during a blood moon?
A lunar eclipse occurs when the Sun, Earth, and Moon line up at full moon, allowing Earth’s shadow to fall across the lunar surface. During a total eclipse, the entire Moon enters the umbra, the darker central part of that shadow.
The Moon usually remains visible rather than disappearing. NASA’s visualization of Earth’s shadow crossing the Moon shows the disk gradually darkening, turning red during totality, and brightening again as it leaves the shadow.
Why does the Moon turn red?
Earth blocks the sunlight that would normally illuminate a full moon, but a small amount of light takes a longer route through the edge of our atmosphere. Shorter blue and violet wavelengths scatter more easily, while more red and orange light is bent into Earth’s shadow and reaches the Moon.
The exact color varies from one eclipse to another. Dust, clouds, smoke, and volcanic aerosols in Earth’s atmosphere can produce anything from a bright copper Moon to one that is dark brown and difficult to see.
Astronomers use the five-point Danjon scale to record that variation. An L=0 eclipse is extremely dark, while an L=4 eclipse is bright copper or orange with a lighter rim.
Total, partial, and penumbral lunar eclipses
Earth’s shadow has a faint outer region called the penumbra and a much darker inner region called the umbra. The type of eclipse depends on how deeply the Moon enters those shadows.
- Penumbral: The Moon passes through Earth’s outer shadow. What you may see: A slight dimming that can be difficult to notice.
- Partial: Part of the Moon enters the umbra. What you may see: A dark curve or “bite” spreads across part of the disk.
- Total: The entire Moon enters the umbra. What you may see: The Moon darkens and usually turns red or copper.
Why isn’t there a blood moon every full moon?
The Moon’s orbit is tilted by about 5 degrees relative to Earth’s path around the Sun. Most full moons therefore pass a little above or below Earth’s shadow.
Lunar eclipses happen during eclipse seasons, when a full moon passes close to one of the two points where its orbit crosses Earth’s orbital plane. That alignment repeats often enough to produce regular eclipses, but not at every full moon.
How to see a blood moon
Unlike a solar eclipse, a lunar eclipse is safe to watch with your eyes, binoculars, or a telescope. You don’t need eclipse glasses, and no special equipment is required.
Check your local viewing time and find a clear view of the Moon, preferrably away from bright lights so the dim Moon and nearby stars are easier to see.
The penumbral stage is subtle and may pass unnoticed. The partial stage is easier to follow, while totality is when the entire Moon takes on its deepest color.
Other uses of the term
Blood Moon occasionally appears as an alternative name for October’s full moon, which you can read more about in our Hunter’s Moon article.
The term also appeared frequently around the 2014–2015 lunar tetrad, a sequence of four total lunar eclipses, often described as four blood moons.