The following information has been provided by the American Academy of Ophthalmology (AAO):
On Monday, Aug. 21, 2017, a solar eclipse will be visible across North America (weather permitting). The whole continent will experience a partial eclipse lasting 2 to 3 hours. Halfway through the event, anyone within a roughly 70-mile-wide path from Oregon to South Carolina will experience a brief total eclipse. At that point, the moon will completely cover the face of the sun for up to 2 minutes 40 seconds. According to NASA, the metropolitan Washington, DC area will experience a partial solar eclipse from about 79 percent of the sun obscured to more than 90 percent. The farther south you are, the more the sun will be obscured.
A truly awe-inspiring event, a solar eclipse is when the moon blocks any part of the sun from our view. The bright face of the sun is covered gradually by the moon during a partial eclipse, lasting a few hours. During the brief period of a total eclipse when the moon fully covers the sun (only a couple of minutes), the light of day gives way to a deep twilight sky. The sun’s outer atmosphere (called the solar corona) gradually appears, glowing like a halo around the moon in front of it. Bright stars and planets become more visible in the sky.
Watching a solar eclipse is a memorable experience, but looking directly at the sun can seriously damage your eyes. Staring at the sun for even a short time without wearing the right eye protection can damage your retina permanently. It can even cause blindness, called solar retinopathy.
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.
Steps to follow for safely watching a solar eclipse:
- Carefully look at your solar filter or eclipse glasses before using them. If you see any scratches or damage, do not use them.
- Always read and follow all directions that come with the solar filter or eclipse glasses. Help children to be sure they use handheld solar viewers and eclipse glasses correctly.
- 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.
- 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.
- 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.
- 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 handheld viewers, check out the American Astronomical Society.