Eclipses Solar eclipse
Solar eclipses
A shadow path a few hundred kilometres wide
The Moon covers the Sun, and only the narrow track of its umbra sees totality.
- Conditions
- New Moon, with the Moon near a node
- Width of totality
- Usually under 300 km
- Duration of totality
- Usually under 7.5 minutes
01 / Overview
Meet Solar eclipses
A solar eclipse happens at new Moon, when the Moon also lies near a node of the ecliptic. Its umbra sweeps a track across the ground usually less than 300 km wide, and only inside that track is the eclipse total; the far larger area around it sees a partial eclipse. When the Moon is a little further away, the umbra falls short of the surface and the eclipse is annular.
Total, annular and hybrid
The Moon’s apparent diameter runs from about 29.4′ to 33.5′ with distance, the Sun’s from about 31.6′ to 32.7′. When the Moon wins, the eclipse is total; when it loses, a ring of sunlight remains and the eclipse is annular. A few eclipses are total in the middle of the track and annular at both ends — a hybrid.
The saros
Similar eclipses repeat every 6,585.3 days — about 18 years, 11 days and 8 hours — a cycle called the saros. That extra third of a day shifts each track roughly 120° of longitude westward, which is why any one place waits so long for its next totality.
02 / Key data
Core parameters
- Conditions
- New Moon, with the Moon near a node
- Width of totality
- Usually under 300 km
- Duration of totality
- Usually under 7.5 minutes
- The saros
- About 18 years, 11 days, 8 hours
- Recurrence
- Two to five times a year
Data and calculation notes
Active periods, peak dates and rates are multi-year averages; each year differs a little, so plan against the forecast issued for the year in question.
03 / Observing tips
How to watch
- Outside totality itself, a certified solar filter is required at every moment.
- Sunglasses, exposed film and under-filtered gear are all unsafe.
- The observatory’s sky-event planner lists future solar eclipses and can jump to maximum.
04 / Sources