News release: Eclipse Eye Safety

Tim Baker, MU Extension Horticulture Specialist
102 N. Main, Suite 1, Gallatin, MO 64640
660-663-3232, bakert@missouri.edu

Release Date: August 10, 2017
Headline: Eclipse Eye Safety

The total solar eclipse is almost here! Hopefully you have made a list of everything you will need that day. At the top of the list should be approved safety glasses for viewing the sun.

Through all the partial phases of the eclipse, you definitely need approved eye protection. Anything less could damage your eyes or cause blindness. There are lots of unapproved ideas on how to view the sun. Don’t try them! Your vision is too important to take a chance.

Sunglasses, for example, do not darken the sun enough to use.  Smoked glass also should not be used for many reasons, including the fact that they may let damaging infrared and ultraviolet light through.

Some older techniques include using fully exposed black and white silver-based photographic film. Even that is not considered safe by most authorities today.

Some sources say that welding lenses are safe if they are dense enough. Most of them say to use a #12 to #14.  Anything less is not safe. I would still be careful with them, and would prefer approved glasses, which have been verified to be compliant with the ISO 12312-2 international safety standard.

What is the problem with unapproved filters? Even if you may be able to look at the sun without discomfort, they may be letting through wavelengths of sunlight that will cause damage.  Approved filters have been tested not only for visible light, but also wavelengths in the infrared (IR) and ultraviolet (UV) spectrum. These wavelengths will not be visible to your eye. So even though there may not be any discomfort to your eyes, if IR and UV are getting through, the light may still cause damage.

I have seen filters being sold for cameras that are heavy neutral density (ND) filters. When I see that, I wonder if they have been tested for IR and UV, even if coming from a reputable filter manufacturer.  I have read astronomers that say not to use ND filters. I would stick with solar filters made by a telescope manufacturer.

Even solar glasses that are compliant with ISO 12312-2 should be carefully inspected for pinholes and scratches.  They won’t do their job safely if defective.

Finally, I should mention that there have been reports of bogus solar glasses which are not safe. Some scam artists are even falsely marketing their products as being ISO compliant.  I have several articles on that topic on my web page which can be found at: http://extension.missouri.edu/nwhort/solar.aspx

Enjoy the show… but be SAFE!