Solar eclipse glasses: How to check safety and use them correctly

The great North American total solar eclipse of April 8 is over, but remember: Never observe the sun without proper protection. Get a pair of safe solar eclipse glasses from reputable dealers we recommend down below to ensure you and your family remain safe when observing future solar eclipses.

Have them already? Read on as we show you how to check if they're real or fake solar eclipse glasses and how to look after them as well as use them properly during a solar eclipse.

While there are lots of exciting ways to observe the sun, the relative infrequency of solar eclipses makes them particularly thrilling events to witness first-hand. Solar eclipses can take on different forms and so keep an eye out for strange eclipse phenomena. These forms include partial eclipses, where the moon partially covers the sun and creates a crescent shape, total eclipses, where the moon completely obscures the sun, and annular eclipses, where the moon appears smaller than the sun and creates a ring of fire around it.

Learn about the stages of a total solar eclipse to be sure you spot everything when the next one comes around. You can find information on upcoming eclipses happening wherever you are in the world in our when is the next eclipse guide or via a helpful graphic that charts the projected course of each eclipse on Timeanddate.com.

Solar eclipse glasses deals October 2024

• Amazon: Celestron solar eclipse glasses
• Target: Discounted ISO-certified solar glasses
• Walmart: Solar glasses, binoculars and filters available
• Staples: Solar eclipse multipack available
• Best Buy: Solar glasses, viewers, telescopes and binoculars
• B&H Photo Video: Single and multipack eclipse glasses
• Adorama: Solar eclipse glasses and filter adapter kits

Regardless of the type of eclipse you're looking to view, it is essential that you use adequate eye protection whenever you look directly at the sun to avoid causing permanent and irreparable damage to your retinas. 

While it might be tempting to pick up a cheap pair of solar-eclipse glasses from places like Amazon or eBay, this puts you at significant risk of buying unsafe or counterfeit glasses that won't provide your eyes with adequate protection. Instead, we recommend buying from one of the reputable sellers featured on this page, or from others that have been approved by the American Astronomical Society, to ensure that they meet current safety standards.

If you're interested in solar binoculars, telescopes or filter adapters be sure to check out our guide to the Best solar viewing kit for the solar eclipse.

Safety standards

Wherever you buy from, it's extremely important to check the safety standards of any glasses you plan to use to view a solar eclipse. Even if a product looks like suitable solar eye protection, that doesn't mean that it's been designed to block out enough harmful radiation to keep your eyes safe when looking at the sun head-on (which is very different to just going outside on a sunny day).

It's best to look for a product that is labeled with 'ISO', which stands for the International Organization for Standardization.

The ISO is an independent organization that writes safety and quality standards for all kinds of things, including eyewear, health care, food production and more based on a broad consensus of the scientific community. If you find eclipse glasses or other solar viewers that aren't labeled 'ISO', then they aren't guaranteed to protect your eyes the way they should.

ISO-approved solar-eclipse glasses must meet certain safety requirements:

• No more than 0.00032 percent of the sun's light may be transmitted through the filters.
• The filters must be free of any defects, such as scratches, bubbles and dents.
• Handheld viewers must be large enough to cover both eyes.
• Labels on the viewers (or packaging) must include the name of the manufacturer, instructions for safe use and warnings of the dangers of improper use.

Where to find ISO-approved eclipse viewers

According to Rick Fienberg, press officer for the American Astronomical Society (AAS), most ISO-approved eclipse glasses use solar filters manufactured by AstroSolar and Thousand Oaks Optical. However, he did note that several different retailers sell eclipse glasses and handheld filters that are approved by the ISO.

The AAS has published a list of reputable vendors and manufacturers of eclipse glasses that includes Lunt Solar Systems, American Paper Optics and Rainbow Symphony.

Sunglasses simply won't do

Eclipse glasses and sunglasses might look somewhat similar, but they are made of very different materials. You should never look directly at the sun while wearing sunglasses, no matter how tinted your lenses may be.

"Normal sunglasses typically let in between 10 and 20 percent of daylight… but that's still way too bright," Fienberg told Space.com. "The filters that are made for looking at the sun are typically 100,000 times darker."

Sunglasses tend to be made of glass, plastic or some kind of polycarbonate material, while solar filters are made of one of two materials: polyester film coated in aluminum, or something called 'black polymer', Fienberg explained. Most eclipse glasses and solar viewers use the black polymer, which is a flexible resin infused with carbon particles. Both types of filters will reduce visible light down to safe levels.

Welding goggles

Welders planning to observe the solar eclipse may or may not be in luck, as some welding filters will adequately protect your eyes from the sun. But, please, double-check to make sure that the goggles you intend to use are the right kind.

"There is a particular circumstance in which it's safe," Fienberg said. "We don't recommend it because it's too easy to get the wrong kind of welding filter." Only goggles made for electric arc welding can be used to observe the sun, and they must have a shade scale number of 12 or higher. Shade 13 is ideal for solar viewing, but that shade is typically not sold in stores, Fienberg added.

Chasing the total solar eclipse

If you're lucky enough to catch a total solar eclipse within the narrow path of totality, then it is safe to remove your protective glasses only while the moon is fully obscuring the sun. "In fact, if you keep your filters on during totality, you won't see anything" because they block out almost all light," Fienberg said. Just be sure to check in advance how long the sun is projected to be completely obscured by the moon (which will usually only be for a few minutes at most) and replace your glasses as soon as the sun starts to reappear to avoid the risk of retinal damage. Remember that it only takes a small part of the sun to be visible to permanently harm your eyes, so if you're watching a partial or annular solar eclipse, you'll need to keep your glasses on the entire time.

This makes total solar eclipses particularly impressive. "A total solar eclipse is truly spectacular and awesome in the true meaning of the word 'awesome', whereas a partial solar eclipse could pass unnoticed," Fienberg said. "Even if you do have a solar filter and watch the sun turn into a thin crescent, it's nowhere near as exciting as a total eclipse, because you miss all the really spectacular phenomena that are associated with totality. It doesn't get dark, you don't see the corona, you don't see bright red prominences of gas jetting off from the edge of the sun. It's just not the same at all."

Editor's Note: If you snap an amazing picture of a solar eclipse, and would like to share it with Space.com's readers, send your photos, comments, and your name and location to spacephotos@space.com.