The short answer
To watch a solar eclipse safely, look at the Sun only through solar viewers or eclipse glasses that meet the ISO 12312-2 international safety standard, or watch indirectly with a pinhole projector. Ordinary sunglasses, however dark, are not safe. The only time you can look at the Sun without protection is during the brief total phase of a total solar eclipse, and you must put your viewer back on the moment the Sun starts to reappear. Lunar eclipses are completely safe to watch with your eyes, binoculars or a telescope.
Why the Sun is dangerous
Looking at the Sun, even when most of it is covered by the Moon, can permanently damage the retina at the back of your eye. The damage is called solar retinopathy. The retina has no pain receptors, so you won’t feel it happening; symptoms such as blurred or missing spots in your vision can appear hours later and may never go away.
An eclipse isn’t more dangerous than the everyday Sun. It’s dangerous because it tempts people to stare at something they normally wouldn’t. Even when 99 percent of the Sun is covered, the remaining sliver is intensely bright.
Safe ways to watch
- Certified eclipse glasses or handheld viewers. They must meet ISO 12312-2. Buy from a reputable supplier; counterfeits labeled with the standard have been sold. The American Astronomical Society keeps a list of suppliers it has checked. Through a proper viewer, the Sun looks like a comfortable orange or white disk and nothing else is visible.
- Inspect before every use. Throw them away if the filter is scratched, punctured, torn or separating from the frame.
- Put them on before you look up, and look away before you take them off. Keep wearing your normal glasses underneath if you need them.
- Supervise children at all times so they don’t take viewers off while facing the Sun.
- Pinhole projection. Make a small hole in a piece of card and let sunlight fall through it onto a second card or the ground, with your back to the Sun. You’ll see a small image of the eclipsed Sun. The gaps between leaves on a tree, or a kitchen colander, do the same and make dozens of tiny crescents.
What is never safe
| Item | Why not |
|---|---|
| Sunglasses, even very dark or polarized | They let through far too much light and invisible radiation |
| Stacks of sunglasses | Still not safe |
| Smoked glass, exposed film, CDs, X-ray film | Unreliable and not designed to block the Sun |
| Glancing at the Sun “just for a second” | Damage can happen quickly and without pain |
| Damaged or uncertified “eclipse glasses” | May not block enough light; replace them |
Totality: the one exception
During a total solar eclipse, there is a short period when the Moon covers the Sun completely. Only then, and only if you are inside the narrow path of totality, is it safe to look with the naked eye. You’ll see the Sun’s pale outer atmosphere, the corona, which is invisible at any other time.
Put your viewer back on as soon as the first bright bead of sunlight reappears at the Moon’s edge. If you’re outside the path, you see only a partial eclipse, and you must use a viewer the whole time.
Annular eclipses, when the Moon is too small to cover the Sun and leaves a bright ring, never have a safe naked-eye phase. Keep your viewer on throughout. For dates, paths and local circumstances, see eclipses.
Cameras, binoculars and telescopes
Binoculars, telescopes and camera lenses concentrate sunlight. Never look through any of them at the Sun while wearing eclipse glasses: the concentrated light can destroy the glasses’ filter and your eye in an instant.
To observe the Sun with optics, you need a dedicated solar filter made for that instrument, fitted securely over the front, the end pointing at the Sun, never at the eyepiece. If you’re new to this, the safest choice is to enjoy the eclipse with certified glasses and leave magnified views to an experienced observer with proper equipment, such as at a public eclipse event.
Lunar eclipses are safe
A lunar eclipse happens when the Moon passes into Earth’s shadow. You’re looking at a dimmed Moon, not the Sun, so no protection is needed at any stage. During a total lunar eclipse the Moon often turns copper or red, lit by sunlight bent through Earth’s atmosphere. Binoculars make the colors richer. Anyone on the night side of Earth can see it, so lunar eclipses are far more widely visible than solar ones. Check the Moon page and eclipses for upcoming ones.