In this article
The rule that matters most
Never look at the Sun, even when it is mostly covered, without proper eclipse glasses that meet the ISO 12312-2 standard. A thin crescent is still enough sunlight to burn the retina, and the damage can be permanent.
Solar retinopathy is often painless. You may notice nothing at the time, and the blurred or missing patch in your vision shows up hours later. That is why caution has to come before the event, not after.
What is not safe
- Ordinary sunglasses. Even very dark pairs block far too little.
- Smoked glass, CDs and film negatives. They may look dark while letting harmful rays through.
- Binoculars, telescopes and camera viewfinders without a solar filter. They concentrate sunlight and can injure instantly.
- Eclipse glasses stacked on optics. Glasses worn behind a telescope or binoculars do not protect; the filter must go on the front of the lens.
Safe ways to watch
The simplest option is certified glasses. Check the ISO 12312-2 marking, look for scratches or tears before using them, and throw away any that are damaged. Buy from a reputable supplier, since counterfeit glasses exist.
For a hands-off approach, use indirect projection. Poke a small hole in a piece of card and let sunlight fall through onto a second sheet, with your back to the Sun. The gaps between leaves or the holes of a colander also throw dozens of little crescents onto the ground, and none of this risks your eyes.
When you may look without glasses
During a total solar eclipse, and only during the few minutes of totality when the Sun is fully covered, you can look with bare eyes. When the first bead of brilliant light reappears, put your glasses back on immediately.
In an annular or partial solar eclipse there is no safe unprotected moment, so never remove your glasses.
Before and during the day
- Plan your spot. Choose a place with a clear view and room for everyone.
- Supervise children. Help them put on glasses and check they keep them on.
- Protect cameras. A phone or camera needs a solar filter on the lens, or the sensor can be damaged.
- Agree a signal. Decide in advance who calls totality, so nobody guesses.
Lunar eclipses are different
A lunar eclipse needs no protection at all, because you are looking at the dim, reflected light of the Moon. If you want a relaxed first eclipse, start there. The eclipses hub lists the upcoming eclipses of both kinds.
Questions people ask
Can I use two pairs of sunglasses?
No. Stacking sunglasses does not make them safe. Only glasses certified to ISO 12312-2 protect you when looking at the Sun.
What if I looked at the Sun for a moment?
Do not wait for symptoms, since damage can be painless. If your vision seems blurred, spotted or distorted afterwards, see an eye doctor promptly.
Are pinhole projectors really safe?
Yes. You look at the image on a surface, not at the Sun, so no sunlight enters your eyes.