Can you really go blind staring at an eclipse? Tips for safe viewing

On August 21, the moon’s shadow will block the sun from view in a total solar eclipse.

Wherever you are in the United States, you’re going to want to look up, and that’s OK. Every astronomer in the country will tell you to enjoy this rare opportunity. No matter what superstitions you’ve heard, there is no risk to your health due to simply being outside during a total solar eclipse.
But there’s one thing you shouldn’t do, and that’s look at the sun with your naked eye.
Don’t do it. Really.
The only time you can look at the sun with your naked eye is A) if you’re in the path of totality, where the sun will be completely covered by the moon, and B) during those two minutes or less when the sun is completely covered.
During those brief and geographically constrained moments, the brightness of the sun is reduced to that of a full moon, which can be viewed safely without anything over your eyes.
Otherwise, any glimpse of the sun’s brightness is not only uncomfortable, it’s dangerous.
Your face won’t melt off, “Raiders of the Lost Ark”-style, but your eyes could be severely damaged. And, yes, you could go blind.
Looking directly at the powerful brightness of the sun can cause damage to the retina, the light-sensitive part of the eye.
“When you look directly at the sun, the intensity of the light and the focus of the light is so great on the retina that it can cook it,” said Christopher Quinn, president of the American Optometric Association. “If the exposure is great enough, that can and will lead to permanent reduction in vision and even blindness.”
No matter how cute or fancy they may be, wearing your favorite pair of sunglasses — or a whole stack of sunglasses, for any MacGyver wannabes out there — won’t help. You’ll need eclipse glasses, which are regulated by an international safety standard. They’re cheap and widely available, and some libraries are even providing them free.
Whether you use the cardboard eclipse glasses or a handheld card with a single rectangular view, the most important feature is the filter.
Here are safety tips to remember, according to the American Astronomical Society:
  • Always inspect your solar filter before use; if it’s scratched, punctured, torn or otherwise damaged, discard it. Read and follow any instructions printed on or packaged with the filter.
  • Always supervise children using solar filters.
  • If you normally wear eyeglasses, keep them on. Put your eclipse glasses on over them, or hold your handheld viewer in front of them.
  • Stand still and cover your eyes with your eclipse glasses or solar viewer before looking up at the bright sun. After looking at the sun, turn away and remove your filter; do not remove it while looking at the sun.
  • Do not look at the uneclipsed or partially eclipsed sun through an unfiltered camera, telescope, binoculars or other optical device.
  • Similarly, do not look at the sun through a camera, a telescope, binoculars or any other optical device while using your eclipse glasses or handheld solar viewer; the concentrated solar rays could damage the filter and enter your eyes, causing serious injury.
  • Seek expert advice from an astronomer before using a solar filter with a camera, telescope, binoculars or any other optical device; note that solar filters must be attached to the front of any telescope, binoculars, camera lens or other optics.
  • If you are inside the path of totality, remove your solar filter only when the moon completely covers the sun’s bright face and it suddenly gets quite dark. Experience totality and then, as soon as the bright sun begins to reappear, replace your solar viewer to look at the remaining partial phases.
  • Outside the path of totality, you must always use a safe solar filter to view the sun directly.

 

CNN

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