Eclipse Calculator

How It Works

A solar eclipse occurs when the Moon passes between Earth and the Sun, casting a shadow on Earth's surface. Because the Moon's orbit is slightly tilted (5.1°) relative to the ecliptic, eclipses only happen when a new moon occurs near a lunar node — the point where the Moon's orbit crosses the ecliptic plane.

Solar eclipse types depend on the Moon's distance from Earth. When the Moon is near perigee (closest approach), its apparent diameter exceeds the Sun's and produces a total eclipse. Near apogee, the Moon appears smaller, leaving a ring of sunlight visible — an annular eclipse. A hybrid eclipse transitions between total and annular along its path.

A lunar eclipse occurs when Earth's shadow falls on the full moon. The shadow has two zones: the penumbra (partial shadow, where Earth blocks only part of the Sun) and the umbra (full shadow). A total lunar eclipse (blood moon) happens when the Moon passes completely through the umbra. Unlike solar eclipses, lunar eclipses are visible from the entire night side of Earth simultaneously.

Eclipses recur in cycles called the Saros (≈ 18 years 11 days). After one Saros, the Sun, Earth, and Moon return to nearly the same relative geometry, producing a nearly identical eclipse — but shifted about 120° west in longitude, because 18 years 11 days is not an exact number of Earth rotations.

Safe viewing: Never look directly at the Sun during a partial or annular solar eclipse without certified solar eclipse glasses (ISO 12312-2). The only safe time to view a solar eclipse with the naked eye is during the brief period of totality in a total eclipse. Lunar eclipses are completely safe to observe without any eye protection.