Solar eclipse
The Moon’s shadow falls on Earth; type and duration depend on the observer’s path.
Sun, Earth, Moon · alignment
Eclipses
A grounded guide to solar and lunar eclipse geometry, paths of visibility, local circumstances, Saros cycles, and safe observation.
Direct answer
An eclipse requires the Sun, Earth, and Moon to align near the Moon’s orbital nodes. A solar eclipse is highly location-specific and requires certified solar viewing protection outside totality; a lunar eclipse can be seen from much of Earth’s night side when the Moon is above the horizon.
Quick facts
Lunar eclipse
The Moon moves through Earth’s shadow; the event is safe to view with unaided eyes.
Why not monthly
The Moon’s orbit is tilted to the ecliptic, so most new and full Moons miss exact node alignment.
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The Active Transits Sky Map
Current geocentric longitudes. No local rise, set, altitude, direction, weather, or future visibility is inferred.
The phase family is derived from current Sun and Moon longitude. It is not an exact phase-event time, illuminated fraction, moonrise calculation, or local visibility forecast. Void-of-course hours for the two weeks ahead, and the next sign changes, are measured on the Void-of-Course Moon Calendar.
Solar eclipse types and paths
A total solar eclipse occurs where the Moon fully covers the Sun; an annular eclipse leaves a bright ring because the Moon appears too small to cover the solar disk; a partial eclipse hides only part of the Sun. The umbral or antumbral path is narrow, while a much wider region may see a partial phase. A global event date never guarantees the same experience in every city.
Lunar eclipse types
During a penumbral lunar eclipse the Moon passes through Earth’s faint outer shadow. In a partial lunar eclipse part of the Moon enters the dark umbra. In a total lunar eclipse the entire lunar disk enters the umbra and can appear copper or red because Earth’s atmosphere filters and bends sunlight into the shadow. Local visibility still requires the Moon to be above the horizon.
Nodes, eclipse seasons, and recurrence
The Moon’s orbit is inclined by about five degrees to Earth’s orbital plane. Eclipses cluster during periods when the Sun is near one of the lunar nodes, the crossing points of those planes. Saros cycles describe families of broadly similar eclipses after roughly 18 years, but the path shifts; recurrence does not make a past city’s circumstances repeat exactly.
Solar viewing safety
Never look directly at the uneclipsed or partially eclipsed Sun without eclipse glasses or a solar viewer that meets the applicable safety standard and is undamaged. Ordinary sunglasses, smoked glass, exposed film, and camera screens are not safe substitutes. Optical devices require a proper solar filter mounted at the front aperture. Follow NASA and local expert guidance for the specific event.
How to check your circumstances
Use an authoritative eclipse map or table that accepts your location. Confirm contact times, maximum obscuration, solar altitude, and time zone. Check the local weather close to the event and identify a safe, open site in advance. This page does not calculate future eclipse paths from today’s Moon position and does not claim visibility without a location.
Sources and live-data notes
- NASA: Eclipses ↗Physical eclipse geometry, safety, and NASA eclipse resources.
- U.S. Naval Observatory: Astronomical Data ↗Authoritative astronomical data services and event tables.
- U.S. Naval Observatory: Rise, Set, and Twilight Definitions ↗Definitions for location-dependent rise, set, and twilight calculations.
- NASA: Moon phases ↗Phase geometry and the repeating sequence of illuminated lunar appearances.
- The Great Almanac live APISame-origin gateway for the validated hourly current-position snapshot; the upstream source is identified in the response metadata.
Continue through the Sky & Time Almanac
Cluster hubSky & Time AlmanacAll observation guides, live instruments, and source boundaries.
Lunar cycle · geometry firstMoon PhasesExact UTC dates and times of the upcoming new Moons, quarters, and full Moons, with a clear explanation of why the Moon changes shape through its 29.5-day cycle.
Lunar almanac · observed nowMoon TodayRead the Moon’s current geocentric longitude, zodiac degree, approximate phase family, and the limits of non-location-aware lunar data.
Observing calendar · verify locallyCelestial EventsLearn the major kinds of celestial events, how to verify an observing opportunity, and what a current longitude feed can and cannot establish.
Seasonal astronomy · one instantEquinoxes and SolsticesLearn what equinoxes and solstices measure, why their calendar dates shift, and why daylight and season do not behave identically everywhere.
Common questions
Why is there not an eclipse every new and full Moon?
The lunar orbit is tilted relative to the ecliptic. Most lunations pass above or below the alignment needed for an eclipse.
Can I look at a lunar eclipse directly?
Yes. Lunar eclipses are safe to view with unaided eyes. Solar eclipses require event-specific eye safety except during the brief total phase for observers inside the path of totality.
Does the current Moon card predict the next eclipse?
No. A current longitude snapshot is not an eclipse-path calculation or future event table. Use NASA or USNO event resources.
