For the first time in nearly a century, on Aug. 21, a total solar eclipse of the sun will be visible in parts of the contiguous United States.

Depending on where you live, and provided the clouds don’t interfere, you will see the sun partially or, if you’re fortunate enough to be in the “path of totality,” completely disappear behind the moon. And you know what else you’ll see if you aren’t careful?

An eye doctor. That is, if you look up at the eclipse without protection or if you buy counterfeit viewing glasses.

With every major event or crisis, the con artists show up ready to fleece someone. In this case, unscrupulous companies are selling unsafe eyewear. To safely view this spectacular solar event, sunglasses won’t do — no matter how dark the lenses. You also shouldn’t use any other unfiltered devices such as binoculars, cameras or telescopes. The eyewear or handheld viewer you buy needs to have certified solar filters.

Both NASA and the Federal Trade Commission have issued consumer warnings urging people to be sure to purchase the right glasses.

“This rare event will be exciting and even better when you view the eclipse safely,” Alesha Hernandez, the FTC’s consumer education specialist, wrote in a blog post.

You’ve only got a few weeks left to shop, so don’t wait until the last minute and, in your rush, possibly get scammed.

As you shop, look for glasses that are marked “ISO” followed by these numbers: 12312-2. This means they have met a certain international safety standard.

But the ISO label isn’t enough. Dishonest companies know people are being cautioned to look for that stamp of approval. They can easily copy it onto counterfeit glasses. As I browsed online, every seller promised that its glasses were “certified.” So the American Astronomical Society’s Solar Eclipse Task Force has compiled a list of recommended vendors.

I’m not playing around with my eyes and neither should you. This is not the time to skip doing your homework.

You’ll find a list of reputable vendors for solar filters and viewers at eclipse.aas.org/resources/solar-filters. Here are the U.S.-based manufacturers on the list:

American Paper Optics (Eclipser)

Celestron (EclipSmart Glasses &Viewers)

DayStar (Solar Glasses)

Explore Scientific (Solar Eclipse Sun Catcher Glasses)

Lunt Solar Systems (SUNsafe SUNglasses)

Meade Instruments (EclipseView Glasses &Viewers)

Rainbow Symphony (Eclipse Shades)

Thousand Oaks Optical (Silver-Black Polymer &SolarLite)

You’ll find glasses online and in retail stores, including paper and plastic versions, starting at a few dollars for one pair up to about $20 for a multiple pack of glasses.

Read the consumer comments before you buy. When I did, several people who purchased from reputable manufacturers complained that their glasses arrived damaged. Do not use damaged eyewear to view the eclipse. Return them for a replacement. Even glasses that are scratched or wrinkled should be avoided, according to NASA. The agency also cautions against using eclipse-viewing eyewear that is more than 3 years old.

You can find a full compilation of NASA’s safety information at eclipse2017.nasa.gov/safety. By the way, the agency will have live programming and interactive online content during the eclipse at www.nasa.gov/eclipselive.

There’s lots of money to be made from what’s being called the “Great American Eclipse.” Hotels and camping grounds will be overflowing and — if you can still get a spot — it won’t be cheap. If you can’t afford to travel to the best viewing places, there will be lots of coverage. The Washington Post will have special features for the big day of darkness that will include live blogs, videos, graphics and photos.

Here’s a Post FAQ on what you need to know about the eclipse: wapo.st/2vfn71m. You’ll find more information about why you need to protect your eyes at wapo.st/2vfFC5T. Check your local library system to see if any branches are hosting eclipse events in which free glasses may be distributed (while supplies last of course).

If you’re going to be hardheaded and try to watch the eclipse unprotected, be forewarned you could end up with severe retinal burns. The damage could be temporary or permanent.

Be careful. And don’t let the scammers ruin your excitement during this epic celestial event.

© 2017, Washington Post Writers Group