If there's one thing I can't stress enough about preparing for the 2017 total solar eclipse, its that you should never ever look directly at the sun until it has reached 100 percent eclipse (which will only happen within the path of totality). Even if the sky is dim, and it seems like you could look at it without harming your eyes, you're wrong. You could suffer damage almost immediately.

The AAS says the following about viewing an eclipse:

The only safe way to look directly at the uneclipsed or partially eclipsed Sun is through special-purpose solar filters, such as "eclipse glasses" or handheld solar viewers. Homemade filters or ordinary sunglasses, even very dark ones, are not safe for looking at the Sun; they transmit thousands of times too much sunlight.

When shopping for a pair of viewing glasses, make sure they are ISO certified to meet current eclipse filter guidelines. Don't just buy a pair of shades that are called "Eclipse Viewing Glasses." Even if the manufacturer claims the glasses are ISO certified, you should do just a little more research before making your purchase.

There are actually only a handful companies certified to manufacture eclipse-grade viewing filters in the U.S. The American Astronomical Society (AAS) provides a list of trusted manufacturers that make ISO 12312-2 certified eclipse glasses and filters. I highly recommend checking this list when selecting your glasses. NASA does too.

Warby Parker recently announced on Twitter that it will be giving away ISO 12312-2 certified eclipse viewing glasses at its retail sunglass stores around the country. All you have to do is drop by.

Additionally, Space.com reported that two million free ISO 12312-2 certified eclipse viewing glasses will be given at public libraries across the country.

Dave Mark at The Loop published an email he received from Amazon with a recall notice and advice that he should not use the glasses he purchased to view a solar eclipse. The reason; The seller didn't confirm with Amazon that the filters were sourced from one of the recommended manufacturers.

The letter reads:

We're writing to provide you with important safety information about the eclipse products you purchased on Amazon (order #113-5832038-7027461 for Daylight Sky G021 Plastic Solar Eclipse Glasses with Carry Case, Adult Size, Cool Style and Look, CE and ISO Tested, Safe Solar Viewing, (3 Glasses and 3 Cases), 3 Piece).

To protect your eyes when viewing the sun or an eclipse, NASA and the American Astronomical Society (AAS) advise you to use solar eclipse glasses or other solar filters from recommended manufacturers. Viewing the sun or an eclipse using any other glasses or filters could result in loss of vision or permanent blindness.

Amazon has not received confirmation from the supplier of your order that they sourced the item from a recommended manufacturer. We recommend that you DO NOT use this product to view the sun or the eclipse.

But, this advice should be taken across the board. Don't ever use eclipse glasses that aren't specifically ISO certified and are made by one of the suggested manufacturers. There are businesses and organizations that will offer free eclipse-viewing glasses to people who attend special eclipse parties. Bring the list of manufacturers with you and double-check to make sure they meet the standards.

The International Organization for Standardization (ISO) notes that certified eclipse viewing glasses must meet the following criteria:

  • 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.

Portland-based KGW reported that some of the glasses that Amazon has put on the recall list are actually from certified filter manufacturers on NASA and the AAS list of recommended manufacturers.

Two other U.S.-based Amazon solar eclipse glasses sellers contacted KGW following Amazon's recall. Both said their products were verified as safe and manufactured by companies approved by NASA, but their glasses are still under a recall.

KGW says the owner of one solar eclipse glasses distributor said his glasses come from Thousand Oaks Optical and Baader Planetarium, both of which are on the recommended list. When asked about the confusion regarding sellers that claim their glasses are certified, an Amazon spokesperson told KGW "Customers may have purchased counterfeit versions of legitimate products."

Your eyesight is nothing to take lightly, especially when it comes to looking directly at the sun. The easiest way to know for sure that you're getting the right glasses is to check the list of trusted manufacturers from AAS and try to find eclipse viewing glasses at a brick-and-mortar store near you (eclipse viewing glasses are skyrocketing in price online).

Check out our list of the best gear for viewing the 2017 total solar eclipse

Updated August 15, 2017: Added information about U.S. public libraries and Warby Parker giving away ISO 12312-2 certified eclipse-viewing glasses.