Why You Need Special Glasses to Watch the Eclipse

August 16, 2017, 4:31 PM UTC

Monday, August 21, will be an amazing once-in-a lifetime opportunity to see total solar eclipse — or a prime opportunity to permanently damage your eyes.

By now, you probably know it’s not ok to stare directly into the sun. Although it feels less intuitive, the same rule applies during an eclipse. Even looking at the semi-obscured sun for a few seconds can lead to “eclipse blindness,” i.e. burns on your retina caused by high-intensity visible light. By looking directly at the sun, you are essentially cooking your eyes but because your retina doesn’t have pain sensors, you won’t be able to feel it happening.

The only exception to the above is for people who are watching the eclipse in the path of totality, during the roughly two minute period when the sun is completely covered by the moon. Outside that short window, looking at the (even partially-eclipsed) sun is dangerous.

To avoid long-lasting vision problems, make sure you pick up eclipse glasses before Monday. The glasses, which are specifically designed for viewing the eclipse and regulated by international safety standards, filter out everything but very bright light (no, your sunglasses won’t cut it).

The American Astronomical Society has a list of recommend eclipse glasses vendors, including Lowe’s, Walmart, and Best Buy. Although many of these retailers and vendors on the list have sold out online, options remain for list-minute buyers. Viewers can also potentially pick up a free pair at their local library or at a NASA viewing event.