Common man's understanding of lunar eclipse

But do we really know how often do eclipses happen and when is the next eclipse of the Moon? Do we also know types of eclipse?

All of us know what is an eclipse of the moon? What causes eclipses and why? But do we really know how often do eclipses happen and when is the next eclipse of the Moon? Do we also know types of eclipse? Here are the answers to these questions in a common man's language.

A lunar eclipse occurs when the Moon passes directly behind the Earth into its umbra (shadow). This can occur only when the sun, Earth, and moon are aligned exactly, or very closely so, with the Earth in the middle. Hence, a lunar eclipse can occur only the night of a full moon.

Types of Lunar Eclipses

An eclipse of the Moon (or lunar eclipse) can only occur at Full Moon, and only if the Moon passes through some portion of Earth's shadow. That shadow is actually composed of two cone-shaped components, one nested inside the other. The outer or penumbral shadow is a zone where the Earth blocks part but not all of the Sun's rays from reaching the Moon. In contrast, the inner or umbral shadow is a region where the Earth blocks all direct sunlight from reaching the Moon.

Astronomers recognize three basic types of lunar eclipses:

Penumbral Lunar Eclipse

• The Moon passes through Earth's penumbral shadow.
• These events are of only academic interest because they are subtle and hard to observe.

Partial Lunar Eclipse

• A portion of the Moon passes through Earth's umbral shadow.
• These events are easy to see, even with the unaided eye.

Total Lunar Eclipse

• The entire Moon passes through Earth's umbral shadow.
• These events are quite striking due to the Moon's vibrant red color during the total phase (totality).

How to watch lunar eclipse

Unlike solar eclipses, lunar eclipses are completely safe to watch. You don't need any kind of protective filters. It isn't even necessary to use a telescope. You can watch the lunar eclipse with nothing more than your own two eyes. If you have a pair of binoculars, they will help magnify the view and will make the red coloration brighter and easier to see. A standard pair obinoculars work fine.

Lunar Eclipse Frequency

Penumbral eclipses are of little interest because they are hard to see. If we consider only partial and total lunar eclipses, how often do they occur?

During the five thousand year period from 2000 BCE through 3000 CE, there are 7,718 eclipses of the Moon (partial and total). This averages out to about one and a half eclipses each year. Actually, the number of lunar eclipses in a single year can range from 0 to 3. The last time that 3 total lunar eclipses occurred in one calendar year was in 1982. Partial eclipses slightly outnumber total eclipses by 7 to 6.

The table below lists every lunar eclipse from 2017 through 2020.

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