The only safe way to look directly at the uneclipsed, partially eclipsed, or annularly 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.
A total solar eclipse is about as bright as the full Moon — and just as safe to look at. But the Sun at any other time is dangerously bright; view it only through special-purpose “eclipse glasses” or hand-held solar viewers that meet the ISO 12312-2 international standard for such products. Homemade filters or ordinary sunglasses, even very dark ones, are not safe for looking at the uneclipsed or partially eclipsed Sun. Credit: Charlie Bates, courtesy Mark Margolis / Rainbow Symphony
The American Astronomical Society and NASA have recommended the following companies as sources for ISO-certified solar viewing glasses.