Just a warning to anyone interested in the coming eclipse. Avoid the glasses sold at Canadian Tire. I just bought two pairs of eclipse glasses at Canadian Tire. I decided to test them right after I got outside and immediately noticed an issue. Both glasses have a hazy appearance around the sun.
With proper eclipse glasses the sun should appear crisp and not too bright. You should be able to distinctly see the edge of the sun and even see detail on the surface. There should be no haze of any kind. If you see any kind of haze, immediately take off the glasses and throw them out.
I knew the glasses from Canadian Tire were suspect because they had "NASA APPROVED" on the sides, which is why I bought them. I wanted to test them.
There is no such thing as "NASA APPROVED". NASA doesn't approve or certify anything. If you see that, it's a massive red flag.
One very good trusted source for where to buy eclipse glasses is the American Astronomical Society which has a list of trusted vendors. I myself bought a bulk quantity from solareyewear.ca and have tested the glasses to be working properly.
https://eclipse.aas.org/eye-safety/viewers-filters
Unfortunately, there will be a massive amount of scams going around with eclipse glasses and shady people trying to make a quick buck. Don't risk it and make sure your glasses will protect your eyes.
If someone tries to convince you that their glasses are genuine because they have ISO-12312-2 printed on them, it doesn't matter. I could print that on a pair of toilet paper rolls taped together, but that doesn't mean it'll protect your eyes.
Here are some resources to check out:
https://aas.org/press/american-astronomical-society-warns-counterfeit-fake-eclipse-glasses
I don't know enough to refute this, but I don't think it's worth the risk even if it was
People won't know when it becomes safe to take off the glasses and when they need to put it on again. It's a fairly brief event
Better to keep the glasses on than risk permanent lifelong damage
Having been to a total eclipse before, it's really extremely obvious when it's time and when it's no longer time. It's very different from partial eclipses. You can easily feel the sudden lack of actual sunlight.
Edit: adding on, I'm pretty sure if you keep the glasses on during the actual eclipse you'll see almost nothing, because the outer fringes of the sun still exposed aren't bright enough to show through those lenses.
Interesting, I've only ever seen partials. Thanks!
Like others said, you'll be fine. Also, the eclipse apps out there will tell you when the full eclipse starts and ends... Down to the second.
If you've never seen an eclipse in totality before... Believe me... TOTALLY worth the risk. It's honestly one of the most surreal and breathtaking events you may ever witness. If you've got the chance to see it, you absolutely should.