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What Is a Partial Lunar Eclipse?

Next Partial Lunar Eclipse: Mon, Aug 7, 2017 … See animation

A partial lunar eclipse happens when the Earth moves between the Sun and the Moon, but they are not precisely aligned. Only part of the Moon's visible surface moves into the Earth's shadow.

Illustration image

Partial lunar eclipse, Los Angeles, U.S.

Partial lunar eclipse as seen from Los Angeles, California.


What Causes a Partial Lunar Eclipse?

A partial lunar eclipse occurs when the Earth moves between the Sun and Moon but the 3 celestial bodies do not form a perfectly straight line in space. When that happens, a small part of the Moon's surface is covered by the darkest, central part of the Earth's shadow, called the umbra. The rest of the Moon is covered by the outer part of the Earth's shadow called the penumbra.

Conditions for a Partial Lunar Eclipse

For a partial lunar eclipse to occur, 2 celestial events must happen at the same time:

  • The Moon should be a full Moon.
  • The Sun, Earth and Moon must be aligned in almost a straight line.

Not Every Full Moon Night

Partial lunar eclipses do not happen every full Moon night because of the inclination of the Moon's orbital plane. The Moon's orbital path around the Earth is inclined at an angle of 5° to the Earth's orbital plane (ecliptic) around the Sun. The points where the 2 orbital planes meet are called lunar nodes.

Eclipses can only happen near the lunar nodes. Lunar eclipses occur when a full Moon happens near a lunar node, and solar eclipses take place when a new Moon occurs near a lunar node.

Stages of a Partial Lunar Eclipse

  • Penumbral eclipse begins: The Earth's penumbra starts covering the Moon's surface.
  • Partial eclipse begins: The Earth's umbra starts moving over the Moon.
  • Maximum eclipse: The Earth's umbra covers the outer part of the Moon.
  • Partial eclipse ends: The Earth's umbra no longer covers the outer part of the Moon.
  • Penumbral eclipse ends: The Earth no longer casts a shadow on the Moon. This marks the end of the eclipse.
Lunar Eclipse Partial
Part of the Moon dips into the Earth's umbra during a partial lunar eclipse.
Part of the Moon dips into the Earth's umbra, the deepest part of the shadow, during a partial lunar eclipse.

How to See?

Partial lunar eclipses can be seen across the night-side of the Earth. No special equipment is needed to see a partial lunar eclipse. All you need is the exact date and time for the next eclipse to be seen from where you are, the weather forecast, some warm clothes and a chair to keep you comfortable while you watch the eclipse unfold.

Upcoming 5 Partial Lunar Eclipses

More details about upcoming Eclipses

Topics: Eclipses, Moon, Sun, Astronomy

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Partial Lunar Eclipse

Aug 7, 2017 at 15:50:01 UTCSee more


Lunar Eclipses

  1. When Is the Next Lunar Eclipse?
  2. Total Lunar Eclipse
  3. Why Does the Moon Turn Red?
  4. Partial Lunar Eclipse
  5. Penumbral Lunar Eclipse
  6. Can I See a Lunar Eclipse?
  7. Blood Moon - Total Lunar Eclipse
  8. Magnitude of Eclipses


Solar Eclipses

  1. When Is the Next Solar Eclipse?
  2. Different Types of Eclipses
  3. What Are Solar Eclipses?
  4. How Often Do Solar Eclipses Occur?
  5. Total Solar Eclipses
  6. Partial Solar Eclipses
  7. Annular Solar Eclipses
  8. Hybrid Solar Eclipses
  9. Solar Eclipses in History
  10. Solar Eclipse Myths
  11. Magnitude of Eclipses


Eclipse Shadows

  1. Umbra
  2. Penumbra
  3. Antumbra

Why Are There 3 Shadows?

Eclipse Lookup

Sunrise & Sunset Times

Moonrise & Moonset Times

Moon Phases In Your City

Weather Look-Up

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Why 3 Shadows?

The Earth and the Moon cast 3 different shadows: umbra, penumbra, and antumbra. Why are there 3 types of shadows and how are they defined? more

What Is the Antumbra?

The antumbra is the lighter part of a shadow that forms at a certain distance from the object casting the shadow. It is involved in annular solar eclipses and planet transits. more

Lunar Eclipse Penumbral

What Is the Penumbra?

The penumbra is the lighter outer part of a shadow. The Moon's penumbra causes partial solar eclipses, and the Earth's penumbra is involved in penumbral lunar eclipses. more

What Is the Umbra?

The umbra is the dark center portion of a shadow. The Moon's umbra causes total solar eclipses, and the Earth's umbra is involved in total and partial lunar eclipses. more