When to Use Eclipse Glasses
(Short answer: Any time the Sun is not TOTALLY eclipsed!)
All right, so it’s eclipse day. You’re with everyone that you want to share the eclipse experience with, and you all have your ISO-certified eye protection (we’ll call that “eclipse glasses”) ready to go.
When exactly do you need to use those eclipse glasses to protect your eyes? The answer to this question is critical, because it’s virtually certain that you’ll injure your eyes – perhaps permanently – if you try to look at the Sun at the wrong time without protection.
Too much of anything is usually not good. Water is necessary for life, but if you drink too much of it too quickly, it can actually kill you. Medicine that can save your life can also end it if you take too much. And the Sun’s light is kind of like that, too. We need the Sun to power basically everything on Earth – light, heat, weather, food, even life itself depends completely on the Sun to keep going.
But as we’ve explained on our page about eye safety, the Sun’s light also contains harmful elements. Looking directly at even a tiny fraction of it for any length of time is certain to damage your eyes. Normally, the Sun is way too bright to even consider trying to look at, so we simply don’t try. But during an eclipse, that brightness definitely decreases as more and more of the Sun gets covered up – and so we might be tempted.
But even if 99% or more of the Sun is covered, if you tried to look directly at it you would still be getting 1%, or 0.1% or even 0.01% of that light. That doesn’t sound like a lot, but remember that there are harmful rays coming at you that are invisible – AND, you won’t feel anything since your retinas don’t have pain receptors. Even if the Sun’s light gets dimmed enough (say, by an eclipse!) so that you might be tempted to look at it, there is still enough UV and even bright visible light entering your eyes to cause permanent damage.
So if you want to safely look at the Sun during an eclipse – even one that is 99.99% – you have to block out all the harmful invisible light as well as enough visible light to make it possible to look without risking injury. And that’s why you have to use CERTIFIED eye protection. These filters have been tested and approved (most likely by Dr. Ralph Chou’s certification lab) for direct solar viewing. And if you buy them from reputable outlets (such as eclipse2024.org!) you can be sure that you’re using glasses that – when used according to the instructions – will protect your eyes completely. By looking at the Sun ONLY through the filters contained in your eclipse glasses (or by another indirect means such as projection), you can be sure your eyes will be protected. That way, you’ll also be able to enjoy the next eclipse!
And you have probably guessed by now as to WHEN you should be looking at the Sun through the glasses: ALL THE TIME that the Sun isn’t TOTALLY eclipsed! That’s right, ANY TIME you would be looking at ANY PART of the Sun’s bright round disk (if you tried to look at it), you HAVE to use the eye protection that your certified glasses give you.
Even Baily’s Beads, or the bright diamond ring that happens at 2nd and 3rd contacts represent a small piece of the Sun’s bright disk that’s getting through to your eyes, and so you still should not be looking at them unless it’s through your eclipse glasses.
Between 2nd and 3rd contacts, when the eclipse is fully total and you can see the corona, you can look directly at the Sun without the eclipse glasses. At these times during totality ONLY, the Moon itself is blocking all the Sun’s light! This allows you to stare to your heart’s content, because the Moon is acting as your eye protection! But this is ONLY during totality: Once the bright diamond ring of 3rd contact comes back, then you need to put the glasses back on to watch the waning partial phases.
So, you use the glasses to protect your eyes BEFORE totality, and AFTER totality, but not DURING totality. (Some astronomers even like to call the eclipse glasses “partial eclipse glasses”, because that’s when you use them during an eclipse.)
What that also means for people who are not experiencing totality, is that you have to ALWAYS use the eclipse glasses to observe the Sun. This means that you MUST use certified eclipse glasses to protect your eyes:
- ALL THE TIME, on a day when an eclipse isn’t happening
- ALL THE TIME, even on eclipse day, if you’re not in the path of totality
- ALL THE TIME, if the eclipse is only going to be partial where you’re located
- ALL THE TIME, if the eclipse is annular like the ones in 2021 and 2023.
- On eclipse day, whenever the eclipse isn’t completely total – even if you’re in the path of totality
If you’d like more information on watching the eclipse, please see the instruction booklet we’ve put together. It explains everything in even more detail!
Whatever you do, please remember the most basic rule of all: If ANY PART of the Sun’s bright disk is visible, you MUST use certified eye protection to observe the eclipse. This will ensure that your eclipse experience is both fun … AND SAFE!