Your guide to enjoying eclipses

VERY IMPORTANT! Looking directly at the Sun, without appropriate protection, can lead to serious problems such as partial or complete loss of eyesight.

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An eclipse is a wonder to behold. Although eclipses occur more often than you might think, there aren't many opportunities to admire them. There are four to seven eclipses per year, but only those people along the path of an eclipse are able to see it.

Artist's rendition of a total solar eclipse. (Credit: CSA)

What is an eclipse?

An eclipse occurs when the light of a body outside Earth's atmosphere (Sun, Moon, planets, etc.) is temporarily blocked by another body. Eclipses don't just happen on Earth: they also take place on other planets, like Jupiter and Neptune.

What is a solar eclipse?

A solar eclipse occurs when the Moon comes between the Earth and the Sun, casting a shadow on Earth.

Animation of a solar eclipse (Credit: NASA)

From the locations along the Moon's umbra trajectory, it appears as if the Sun has gone dark. Depending on the distance between the Sun and the Moon and their positions, it is possible to see three kinds of solar eclipses:

  • Total eclipse: the Moon completely covers the Sun
  • Annular eclipse: the Moon is closer to the Sun; hence the Moon appears smaller than the Sun. A ring of light from the Sun is always visible
  • Partial eclipse: the Sun and the Moon are not perfectly aligned, so only a part of the Sun is hidden by the Moon

Artist's rendition of a total solar eclipse. (Credit: CSA)

Artist's rendition of an annular solar eclipse. (Credit: CSA)

Artist's rendition of a partial solar eclipse. (Credit: CSA)

Total solar eclipse of August 21, 2017

On August 21, 2017, a total solar eclipse will cross the entire United States (from west to east). Fourteen US states will be lucky enough to witness it in its totality, and the other US states and Canada will be treated to a partial eclipse.

The path of totality is a narrow corridor approximately 100 to 115 km wide where the Sun will appear to be completely covered by the Moon for a short period of time (between 2 and 3 minutes). This is the most spectacular part of the eclipse, as those who are lucky enough to be in this corridor will be able to see the Sun's corona, the chromosphere, prominences and streamers. Proper eye protection is essential before and after totality.

For those outside the path of totality, the Sun will appear to be partially covered by the Moon (partial eclipse), and proper eye protection is required at all times.

Will this solar eclipse be visible in Canada?

In Canada, a partial eclipse will be seen from almost every Canadian city. See the map below to find out how much of the Sun's surface will be covered by the Moon and at what time it will occur depending on your location.

Time of maximum eclipse for different cities in Canada. (Credit: Canadian Space Agency)

If you are looking for an activity, visit the Royal Astronomical Society of Canada website, which lists multiple solar eclipse events across Canada, and the Rio Tinto Alcan Planetarium website to learn how you can participate in their special event. It will also be possible to see the total solar eclipse on NASA's live video feed.

How to safely watch a solar eclipse

Watching a Solar Eclipse - Grand Canyon Park visitors observed an annular solar eclipse in May 2012. (Credit: US National Park Service)

VERY IMPORTANT! Looking directly at the Sun, without appropriate protection, can lead to serious problems such as partial or complete loss of eyesight.

During a solar eclipse, it is imperative to wear special glasses with filters designed for eclipse watching (ISO 12312-2 international standard) to prevent eye damage. Regular sunglasses will not protect your eyes sufficiently.

There are other ways to watch an eclipse, such as an eclipse projector, which you can easily learn how to make.

Solar eclipse projector – How to build your own eclipse projector. (Credit: Canadian Space Agency)

When watching a partial solar eclipse, proper eye protection is required at all times.

When will the next solar eclipse be visible in Canada?

On August 21, 2017, a partial solar eclipse will be visible in Canada. The next total solar eclipse to be visible in Canada will occur on April 8, 2024, when the path of totality will cross Mexico, the United States and eastern Canada.

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 different 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

Lunar eclipse - Different stages of a lunar eclipse. (Credit: NASA / Rami Daud)

A total lunar eclipse will go through all three stages and will 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. It is always safe to observe a lunar eclipse with the naked eye. No special eye protection is necessary.

The next total lunar eclipse visible from Canada will occur on January 31, 2018 (western North America).

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