I only took nine weeks of Latin, in seventh grade…
Anyway, if you’re planning to get yourself into the path of this month’s New Moon and gawk at the dark spot where the sun was just a minute ago, you might want to double-check your eye protection. Seems some unscrupulous people are looking to cause an epidemic of eclipse-related blindness.
How can you tell if your “eclipse glasses” or handheld solar viewers are safe? It is no longer sufficient to look for the logo of the International Organization for Standardization (ISO) and a label indicating that the product meets the ISO 12312-2 international safety standard for filters for direct viewing of the Sun’s bright face. Why not? Because it now appears that some companies are printing the ISO logo and certification label on fake eclipse glasses and handheld solar viewers made with materials that do not block enough of the Sun’s ultraviolet, visible, and infrared radiation to make them truly safe. Some sellers are even displaying fake test results on their websites to support their bogus claim of compliance with the ISO safety standard.
The American Astronomical Society offers a list of manufacturers it has verified as complying with the safety standard.
Even if your goggles’ manufacturer isn’t on the list though, they may still be safe.
You shouldn’t be able to see anything through a safe solar filter except the Sun itself or something comparably bright, such as the Sun reflected in a mirror, a sunglint off shiny metal, or the filament of a bare incandescent light bulb. If you can see ordinary household light fixtures through your eclipse glasses or handheld viewer, it’s no good. Safe solar filters produce a view of the Sun that is comfortably bright (like the full Moon), in focus, and surrounded by dark sky. If you glance at the Sun through your solar filter and find it uncomfortably bright, out of focus, and surrounded by a murky haze, it’s no good. You should contact the seller and demand a refund or credit for return of the product, then obtain a replacement from one of the sources listed on the AAS’s reputable-vendors page.
Be safe. The eclipse should be awe-inspiring, not vision-impairing. This is one case where “The goggles do nothing!” isn’t funny.