Viewing the Solar Eclipse Safely: And All About Eclipse Glasses

First, when is the upcoming eclipse? The total solar eclipse is on April 8, 2024! See my 2024 Eclipse Guide.

Now, let’s talk about solar eclipses and eye protection. 

Can You Look at a Solar Eclipse?

The short answer for newbies is: No. 

You cannot safely look at the Sun. You need eye protection. Not with regular sunglasses, not with binoculars, not through a camera lens, and not through a telescope. Not in any way except with a special-purpose solar filter secured over the front of the optics.

The longer answer is: Never during partial, only during the brief moment of totality, but you’d better know what you are doing.

MOST of the eclipse event is either 1) the hour-long partial eclipse leading up to 3 minutes of totality or 2) the hour-long partial phase following totality. Of course, this assumes you are smack on that narrow ribbon of darkness that we call the “path of totality.” Most people just see the partial eclipse. 

During the partial phases, when you can see the Sun, it is NEVER safe to look directly at the Sun without specialized eye protection.

Technically, the only time that the Sun can be viewed safely with the naked eye without special filters is during those 3 or so minutes of totality. However, this needs some context …

I’m in touch with a man who suffers permanent eye damage from looking straight at the Sun decades ago. True, he used binoculars, which can cause permanent blindness in just a second or two. But it brings up that ancient eclipse question: what is the actual, unexaggerated danger of simply peering at the Sun directly?

Few articles tell the truth because eyesight is so precious. Editors usually feel it’s better to exaggerate the danger than to state it neutrally. Years ago, when I was with Discover magazine and researched this, the shortest amount of sun-staring I could find that had created a permanent detectable retinal lesion was 30 seconds. That was a man who’d been drinking and staring at the Sun on a bet. Going the other way, we’ve all taken quick looks at the sun during our lives and have not suffered eye damage. So those are the starting points, the limits: A quick fraction-of-second glance won’t harm you, while 30 seconds can damage your retina permanently. In between lies a blurry, dangerous realm, a terra incognita of ill-defined peril, a swampy land you want to avoid.

Contrary to widespread myth, the Sun is not more dangerous when it’s in eclipse. It’s simply when people have a motive for staring at it. In reality, the danger is produced by heat concentrated on the retinal cells. It takes this heat a little bit of time to build up.

So picture the real-time scenario, the quandary. The Moon has increasingly blocked the Sun during the past 50 minutes, and now, through your filter, it looks like a thin sliver, like a slender crescent Moon. In a minute, even this gets reduced in size. You look at the ground around you; it’s getting darker. If you’re within the path of totality, you want to see the famous “diamond ring” that happens just before totality begins. Is it okay to then take a quick squinting glimpse at the Sun?

Some articles say no. But I and other astronomers, including NASA solar system ambassador Charles Fulco, always do. When it’s almost total, we’ve taken quick (no more than a half-second) glimpses up. We immediately look away if we see anything but the start of totality. You’ll be okay if you can be disciplined enough to limit such momentary glimpses to under a half second.

But many don’t have such discipline. And children should never be allowed to try. So the safest route is to play it safe and use your eye protection until nothing at all shows through your filter or the expert in your party shouts, “It’s total now!”

Let’s not make mistakes that could make you blind forever. 

The Right Type of Eclipse Glasses or Filter

Eclipse Glasses

The American Astronomical Society has compiled a list of vendors where you can buy safe eclipse glasses. (Do not go off this list, as there are dangerous knock-offs.)

These inexpensive “eclipse glasses” are made of cardboard with plastic Mylar filters. They work. A four-pack of cardboard types costs about $10. 

The American Astronomical Society says modern eclipse glasses do not expire. If the glasses are compliant with the ISO 12312-2 and have no punctures, scratches, or tears, and the filters/lenses remain attached to the frames, they will last.

Gain, beware of fake, knock-off eclipse glasses; they may not be strong enough to protect your eyes fully. You can test your glasses by simply looking through them. If you’re able to see the light from lamps, headlights, or even reflections of the sun, your glasses are not strong enough! You should only be able to see the sun itself through your glasses. 

If you’re feeling fancy, go for plastic frames, which are sturdier than cardboard.  Again, do not even consider regular sunglasses. Wear the solar shades right until the Sun goes completely behind the Moon.

Make Your Own “Eclipse Glasses”

The cheap commercial eclipse filters made of Mylar plastic are fine. But for the seven total eclipses I’ve led for our tour company, we always purchase welders’ goggle filters in shades 12 or 14. Their optically certified glass allows for a crisp, perfect image, and those filter replacements are only about $2. 

You can ask your Welding supply store to create a 12, 13, or 14 shade by cobbling together a few lighter-shade filters and stacking them. A 14 will be the most comfortable, although a shade 12 is definitely still safe, web misinformation notwithstanding. More common welder filters, such as shade 10, are inadequate. Don’t use them. 

Or, you can create a safe filter by looking through two layers of exposed and developed black-and-white film. It’s what many astronomers used to use and has been well-tested. Those are the inky black strips at the very end of the negatives. But don’t try to look through negatives with images on them. And don’t use color film. And don’t use black and white film unless it’s been exposed and developed. Even then, use a doubled-up layer. Two thicknesses. We’re talking about old-fashioned Kodak products like Plus-X and Tri-X, which contain silver granules that block harmful light. Some newer films don’t have the silver, so only use the older negative strips—the ones you’ve had lying around forever.

Make a Pinhole Viewer

Some people punch a pinhole in a box and let the Sun project its eclipsed image on another interior part of the box. That’s always safe because you’re not looking directly at the Sun. See NASA’s guide on how to make a pinhole camera.

Avoid Smoked Glass and CD Disks

Our grandparents held a piece of glass over a candle flame and let it get black from soot. Was that dangerous? Were they endangering their eyesight? Surprise: Modern testing shows that such smoked glass only transmits 0.0032 percent of the Sun’s visible and invisible radiation. So it WAS adequate for solar viewing.  To paraphrase our parents, “Please don’t smoke glass.” You should avoid it because you never know how deep the soot layer is or whether some has smudged off. Also, avoid such dangerous web suggestions as looking through a CD. The Sun’s image may seem safely dim, but too much infrared (heat) may be arriving on your retina.

What About Binoculars?

NEVER use binoculars during the partial eclipse leading up to totality. The most dangerous is a view through an unfiltered telescope or binoculars. 

But if you are observing totality through binoculars, that’s great. But I’d limit it to the middle section of this short totality. Once you’ve passed the eclipse midpoint, about a minute after the start of totality, I’d put down the binoculars. 

Because the last thing you want is for totality to suddenly end with, say, a diamond ring of full sunlight and for you to be still using that instrument. Don’t let that happen.

Photos: Leave it to the Experts

Never look through your camera lens without a special solar filter, nor while using your eclipse glasses or solar viewer. The concentrated solar rays will damage the filter and enter your eye(s), causing serious injury. 

Even if you buy a special solar filter for your camera, shooting an eclipse is challenging. It requires the photographer to shift from too much light to shooting in the dark when you need a fast lens. 

Therefore, if you’re a beginning photographer, put that camera down during the 2-minute event, soak in the experience, and look at the thousands of photos professionals took after the event.

We want to see this eclipse and also be able to see each other afterward! Are you planning to watch the eclipse?