The total solar eclipse on August 21, 2017 is kind of a big deal.
On August 21, 2017, for the first time in 99 years, a coast-to-coast solar eclipse will be visible across the continental US. This means that just about anyone in those 48 states will be within a day’s drive of seeing a total solar eclipse. In other words, if you will be in the US on August 21, this is pretty much the total solar eclipse of a lifetime.
Depending on where you are in the US, you’ll see either a partial or total eclipse.
But there’s a catch. Looking directly at the sun — even when it’s partially blocked by the moon — is dangerous.
Other than the brief moment when the moon completely blocks the sun (if you’re in the path of totality), the eclipse must be viewed with special solar filters that are certified to meet international safety standards, says Fienberg. (More on those and eclipse-viewing safety shortly.)
So, what exactly happens when you look at the sun? Turns out that although you probably won’t go totally blind, you can get super serious, permanent eye damage in less than 30 seconds. Yikes.
Let’s start with a quick primer on how the eye works.
It’s a part of the retina that is at risk of being damaged by exposure to sunlight.
And unfortunately the macula is uniquely vulnerable to sunlight damage.
And most of the damage is permanent.
Once the retina’s cells have experienced photochemical toxicity, Habash says “there’s not much we can do about it.” Although some of the damage may correct itself over time, and the area around the burn might recover some vision, there’s no real treatment that will reverse the damage. You could be left with permanent, “disabling” vision loss, says Schuman.
Having said all that, there are ways to safely view a solar eclipse.
Here are the the main things to know:
• Regular sunglasses — even really dark ones — will not protect your eyes from sun damage. Just to illustrate how inadequate even the darkest ordinary sunglasses would be for eclipse viewing, according to Fienberg, certified solar eclipse-viewing glasses are 1,000 times darker than ordinary sunglasses. ONE THOUSAND TIMES.
• According to the AAS, you should only view an eclipse through special-purpose solar filters that meet the ISO 12312-2 international standard for these products. You can buy special eclipse glasses or viewers that allow you to look at an eclipse safely.
• If you view an eclipse through binoculars or a telescope that don’t have special eclipse-safe filters, more light is concentrated onto the retina, Fienberg says, which puts your eyes at even more risk. If you want to use binoculars or a telescope (or any optical device including a camera), you must get special eclipse-safe filters for the front lenses.
And by the way, if you’re in the path of totality, there will be a moment when you can remove your special protective lenses: when the moon blocks the sun completely and it gets completely dark. But as soon as the sun begins to reappear, you must put your special glasses back on.