The coming total solar eclipse on Aug. 21 is the first such event that can be widely seen across North America in 100 years.

Watching it can be an educational and memorable experience. But looking directly at the sun can cause permanent damage to your retina, even if you only look for a short time. It can even cause blindness.

There is only one safe way to look directly at the sun, whether during an eclipse or not: through special-purpose solar filters. These solar filters are used in “eclipse glasses” or in hand-held solar viewers. They must meet a very specific worldwide standard known as ISO 12312-2.

Keep in mind that ordinary sunglasses, even very dark ones, or homemade filters are not safe for looking at the sun.

The American Astrological Society and the National Science foundation offers these steps to follow for safely watching the solar eclipse:

1. Carefully look at your solar filter or eclipse glasses before using them. If you see any scratches or damage, do not use them.

2. Always read and follow all directions that come with the solar filter or eclipse glasses. Help children to be sure they use hand-held solar viewers and eclipse glasses correctly.

3. Before looking up at the bright sun, stand still and cover your eyes with your eclipse glasses or solar viewer. After glancing at the sun, turn away and remove your filter — do not remove it while looking at the sun.

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4. The only time that you can look at the sun without a solar viewer is during a total eclipse. When the moon completely covers the sun’s bright face and it suddenly gets dark, you can remove your solar filter to watch this unique experience. Then, as soon as the bright sun begins to reappear very slightly, immediately use your solar viewer again to watch the remaining partial phase of the eclipse.

5. Never look at the uneclipsed or partially eclipsed sun through an unfiltered camera, telescope, binoculars or other similar devices. This is important even if you are wearing eclipse glasses or holding a solar viewer at the same time. The intense solar rays coming through these devices will damage the solar filter and your eyes.

6. Talk with an expert astronomer if you want to use a special solar filter with a camera, a telescope, binoculars or any other optical device.

For information about where to get the proper eyewear or hand-held viewers, check out the American Astronomical Society.

Source: American Astronomical Society