Your guide to lunar eclipses
Artist's rendition of a total lunar eclipse. (Credit: CSA)
What is a lunar eclipse?
A lunar eclipse occurs when Earth is in between the Moon and the Sun. The Moon passes through the shadow cast by Earth. This phenomenon can only happen during a full moon, when the Moon is on the opposite side of Earth than the Sun. Unlike solar eclipses, lunar eclipses can be seen by practically an entire hemisphere, which means that a much larger number of people can see them for a longer period of time.
Animation of a lunar eclipse (Credit: NASA)
During a lunar eclipse, Earth's shadow consists of the umbra (inner part, where there is no sunlight) and the penumbra (outer part, where there is some sunlight). Depending on the Moon's trajectory, there can be three types of lunar eclipses:
- Penumbral eclipse: the Moon crosses Earth's penumbra
- Partial eclipse: the Moon partially crosses Earth's umbra
- Total eclipse: the Moon completely crosses Earth's umbra
Different stages of a lunar eclipse. (Credit: CSA)
A total lunar eclipse will go through all three stages and will usually last between 30 and 60 minutes. Even during a total lunar eclipse, the Moon is never completely invisible. Sunlight is refracted through the Earth's atmosphere and gives the Moon a red hue, which is where the name Blood Moon comes from.
In order for a lunar eclipse to happen, there must be a full moon. Depending on the time of day and your location (and obviously, the cloud coverage!), you may be able to see the entire eclipse or only part of it. If the eclipse starts shortly after the Moon rises, you will see the whole thing. If the eclipse starts just before the Moon sets, you will only see the first part of it.
How to watch a lunar eclipse
Lunar eclipses are one of the most easily observable astronomical phenomena because you do not need any equipment to observe them. However, you can use binoculars or a small telescope to see more details. You can even take a photo of a lunar eclipse with your cell phone under the right circumstances.
Contrary to solar eclipses, it is safe to observe a lunar eclipse with the naked eye. No special eye protection is necessary.
How often do lunar eclipses occur?
There are on average two lunar eclipses per year, although there can be as many as three to five of them in a year. A total lunar eclipse, also called a Blood Moon, happens in 37.3% of all lunar eclipses.
When will the next lunar eclipse be visible in Canada?
The next total lunar eclipses will be visible in Canada on , and .
In this time-lapse video, watch the different stages of a total lunar eclipse. (Credit: CSA)