How to Watch an Eclipse Safely

Earth, the Sun, and the Moon are coming into alignment. A solar eclipse will be happening near you. What do you need to do to view the eclipse safely?

The first thing to know is you should not look directly at the Sun. You may think that much of the Sun is going to be covered where you are. Surely, it’s not so bad to look at the Sun when, for example, it’s 85 percent covered. That’s a lot less light, right?

The problem with that is that the Sun is very, very, very bright, and even when only a small percentage is uncovered, the Sun is still very bright. During a solar eclipse, when it gets darker, your pupils dilate, letting in even more light. Your retina, the tissue at the back of your eye, is not designed to look at the Sun. The retina has no pain receptors, and you won’t know that you’ve damaged it until hours or days later. Damage to the retina from looking at the Sun is called solar retinopathy and can lead to blurred vision, altered color vision, or even some loss of central vision. Children’s eyes let in more light than adult’s eyes, so they are especially vulnerable.

So how can you watch a solar eclipse safely? There are several ways. You can observe it indirectly by projecting an image of the Sun onto another surface. You can do that by making a pinhole in one side of a box and projecting the image on the opposite side with the Sun behind you. You can use something with a lot of holes in it, such as a colander, to project many images of the eclipse onto the ground.

You can observe it directly only through special eclipse glasses or optical filters. These glasses or filters should conform to the ISO 12312-2 standard. Ordinary sunglasses should not be used, and you should never look directly at the Sun through binoculars or telescopes that do not have solar filters. The American Astronomical Society has a list of suppliers of filters and viewers that are safe to use.

If you are in the path of totality, you can take off your eclipse glasses during the brief period when the Sun is completely covered by the Moon. However, as soon as the Sun reappears, you should resume using your eclipse glasses or filters.