The term solar filters can be used to designate any type of device used to filter the harmful energy produced by the sun that can lead to temporary or, less commonly, permanent vision problems. While many people assume that these types of glasses or hand held devices are necessary only in an eclipse, they are actually essential any time that someone is looking directly at the sun.
In fact, NASA recommends using approved solar filters of some type for all types of eclipses including partial, annual and the initial and ending phases of a full eclipse. It is safe to look directly at the sun without using eye protection only during the few seconds to minutes of a full eclipse, and this provides the best look at the corona of the sun and all the various colors.
The Risk of Homemade Solar Filters
There are many different do-it-yourself projects on how to construct your own solar filters at home. The problem is that if these are not done correctly, of if you try to substitute something different than what is recommended, temporary or permanent eye damage can occur. Even looking at just 1% of the sun when just before the total eclipse or as the eclipse is ending can be enough to damage the eye.
There are also a lot of myths out there about what is appropriate to use as solar filters. Sunglasses are not effective, even those polarized glasses, and no type of film or x-ray film is a safe viewing option. Welder’s glass is acceptable, but only a 14 or greater option can be used, and this is often more expensive than a comfortable and stylish type of hand held filter or a pair of specially designed eclipse viewing glasses.
What Makes Solar Filters Different?
It is important to realize that solar filters products that are available to view an eclipse are not just dark glass that shields out the light. These various types of lightweight, reusable glasses are actually designed with specialized layers of different materials in the lens. These layers can include chromium or aluminum, or in some cases silver, that actually blocks the ultraviolet and the infrared energy of the sun as well as the visible light.
The biggest concern for most people is not for adults using solar filters, but for children failing to understand the importance and trying to look at the sun for too long or too soon during the eclipse. By using glasses or hand held filters that are unique, lightweight and comfortable the kids are much more likely to keep them in place, making solar eclipse viewing much safer.
