Two ways to see a partial eclipse
A partial solar eclipse can happen in two different situations.
A purely partial eclipse. Sometimes the Moon’s dark central shadow, the umbra, misses Earth entirely, passing just above or below the planet. Only the lighter outer shadow, the penumbra, touches Earth, so nobody anywhere sees a total or annular eclipse. These eclipses tend to be seen from high northern or southern latitudes, because that is where the penumbra brushes the planet.
The partial zone of a central eclipse. During a total solar eclipse or an annular solar eclipse, the central path is narrow, but the penumbra covers a region thousands of kilometers wide. Everyone in that wider area sees a partial eclipse. This is why most people who have seen a solar eclipse have seen a partial one.
Why the Moon covers only part of the Sun
At new Moon, the Moon lies roughly between the Sun and Earth, but because its orbit is tilted by about 5 degrees, it usually passes above or below the Sun as seen from Earth. When the alignment is close but not perfect, the Moon clips part of the solar disk. The closer you are to the center line of the shadow, the more of the Sun is hidden.
Measuring a partial eclipse
Two numbers describe how deep a partial eclipse is:
- Magnitude: the fraction of the Sun’s diameter covered by the Moon. A magnitude of 0.5 means the Moon reaches halfway across the Sun.
- Obscuration: the fraction of the Sun’s area that is covered. Because the Sun is round, obscuration is always lower than magnitude for a partial eclipse.
A partial eclipse with magnitude 0.5 covers well under half the Sun’s area. The difference between the two measures is explained in eclipse magnitude.
What you notice
A shallow partial eclipse can pass unnoticed unless you know to look. Deeper eclipses bring subtle changes:
- Crescent images: gaps between leaves on a tree act like tiny pinholes and cast hundreds of small crescent Suns on the ground.
- Sharper shadows: as the visible Sun narrows into a crescent, the edges of shadows in one direction become crisper.
- Slightly dimmer, cooler light when a large share of the Sun is covered, with a hint of an unusual, metallic quality to daylight.
There is no corona, no darkness like night and no stars. The Sun’s remaining surface is still blindingly bright.
Safety: no safe moment without protection
A partial solar eclipse is never safe to view directly at any stage. The exposed part of the Sun is just as intense as on an ordinary day, and staring at it can cause lasting eye damage, often without any pain at the time. Safe options include:
- Certified solar eclipse glasses or handheld solar viewers.
- Telescopes and binoculars only with a proper solar filter fitted securely over the front.
- Indirect viewing with a pinhole projector or a colander that projects crescents onto a card.
Never use a camera, phone, binoculars or telescope pointed at the Sun without a front solar filter, even while wearing eclipse glasses. Read the full guidance in solar eclipse eye safety.
How often partial eclipses happen
Purely partial eclipses make up about a third of all solar eclipses, and a partial phase is part of every solar eclipse. Taken together, that makes a partial solar eclipse by far the most likely kind to be visible from wherever you live. Upcoming eclipses, with the regions where each is visible, are listed on the eclipse calendar.
Partial eclipses at sunrise and sunset
When an eclipse happens close to sunrise or sunset at your location, you may see the Sun rise or set while partially covered, sometimes shaped like horns. These events can make striking photographs, but the same safety rules apply. A low Sun can still harm your eyes, so keep using a proper solar filter or projection, and photograph only with a filter on the lens.