What is a Blood Moon?
“Blood Moon” is a popular name for the Moon during the total stage of a lunar eclipse. The colour can range from copper and orange to deep red, depending on Earth's atmosphere and the observer's viewing conditions.
Why the eclipsed Moon looks red
Earth blocks direct sunlight from reaching the Moon during totality. Some sunlight passes through the edge of Earth's atmosphere, where shorter blue wavelengths are scattered more strongly. The remaining red and orange light is refracted into Earth's shadow and illuminates the Moon.
The result is not one fixed shade. Dust, cloud and aerosols in Earth's atmosphere affect the eclipse, while cameras record different colours according to exposure, white balance, lens and image processing.
Is every full Moon a Blood Moon?
No. A lunar eclipse requires the Sun, Earth and Moon to align closely enough for the Moon to cross Earth's shadow. Most full Moons pass north or south of that shadow because the Moon's orbit is tilted relative to Earth's orbit around the Sun.
Our Moon phase schedule shows full Moon dates, but a phase calendar alone cannot establish whether an eclipse occurs or where it is visible.
Where to check eclipse dates and visibility
Use an eclipse authority for contact times, maps and local visibility. Reliable starting points include the NASA lunar eclipse guide and the US Naval Observatory lunar eclipse data. Visibility depends on both the eclipse geometry and whether the Moon is above your horizon at the relevant time.