Do NOT use eclipse glasses to look through the back of binoculars, telescopes, or a camera viewfinder. It is incredibly dangerous. Ignore the foolish and totally irresponsible advice on the internet that you might get away with it. Just don’t do it.
The Safe and Unsafe Use of Solar Eclipse Glasses
Binoculars, telephotos lenses, and telescopes can focus the light on the very thin surface of the eclipse material, burn through it in an instant and burn your eyes. It would be like someone taking a magnifying glass and focusing the sunlight on the surface of your eye. You will having searing pain and terrible eye damage. Every responsible scientific and medical site warns against this practice.
The only safe way to use solar eclipse glasses is by themselves. If you wear prescription glasses, leave them on. Put the eclipse glasses in front of the lenses of your regular glasses so the sunlight goes through the eclipse glasses first, just like the weird dark glasses you get from the eye doctor to wear in front of your regular glasses after your eyes have been dilated.
The Safe and Unsafe Use of Solar Eclipse Filters and Solar Filter Materials
The same goes for solar filters and solar filter materials. Don’t put them over the back (eyepiece end) of your binoculars, telescope, or camera eyepiece. The only safe place to use solar filter material is on the very front of the binoculars, telescope, or telephoto lens. Some lenses have a filter slot toward the back of the lens. This is fine for most filters but not for a solar filter. The sunlight coming through the front of the lens could burn through the solar filter in the filter slot. Just don’t do it.
Amazon and other online markets have been flooded with unsafe, counterfeit eclipse glasses. You can learn how to buy safe eclipse glasses and other eclipse items here.
Direct Viewing with a White Light Solar Filter
If you were fortunate enough to buy a white light solar filter or solar filter material from Thousand Oaks Optical or one of their safe vendors, you can also use it view the sun. Hold the shiny side of the material toward the sun. Cover your other eye. DayStar (photo immediately above) is one of the safe vendors that uses white light solar filter material from Thousand Oaks Optical when they make their cardboard mounted filters.
You can put white light solar filters and solar filter material on the front of binoculars, telephotos lenses, and telescopes. Do NOT put white light solar filter material on the back side of binoculars, telescopes, camera viewfinders, or in the filter slot at the back of a lens.
Do not buy white light solar filter material that is currently offered on Amazon by vendors who are not known to be safe. The market has been flooded with fakes. Buy only from AAS approved vendors.
High Density Solar Filters
If you bought a high density filter to photograph the sun, it is safe for your camera to take pictures (but only in Live View mode) but it is NOT safe for looking at the sun, or for looking through the viewfinder of your camera.
More information on safely using high density filters is at the links below.
Are Welding Filters Safe for the Eclipse?
This advice is from the American Astronomical Society web site.
“What about welding filters? The only ones that are safe for direct viewing of the Sun with your eyes are those of Shade 12 or higher. These are much darker than the filters used for most kinds of welding. If you have an old welder’s helmet around the house and are thinking of using it to view the Sun, make sure you know the filter’s shade number. If it’s less than 12 (and it probably is), don’t even think about using it to look at the Sun. Many people find the Sun too bright even in a Shade 12 filter, and some find the Sun too dim in a Shade 14 filter — but Shade 13 filters are uncommon and can be hard to find. Our Reputable Vendors of Solar Filters & Viewers page doesn’t list any suppliers of welder’s filters, only suppliers of special-purpose filters made for viewing the Sun.”
Eye Safety and the Models
For the illustrations at the top of the article, Erin was wearing eclipse glasses from Celestron. She was looking through eclipse binoculars also by Celestron. The lens on the camera she was looking through had a Thousand Oaks Optical white light solar filter on the front. In other words, I took every precaution to keep her eyes safe. I would never risk someone’s eyesight by having them wear eclipse glasses and look through normal binoculars or a long lens without a white light solar filter in place.
For the record, she couldn’t see a thing looking through the combined density of two solar filters. When we were done with the photo shoot for this article, she took off the eclipse glasses and checked out the image of the sun on the camera LCD in Live View mode.
John is an experienced amateur astronomer and photographer. With his DayStar solar filter on the front of his lens John has been photographing sunspots crossing the surface of the sun.
Celestron, Thousand Oaks Optical, and DayStar are all AAS approved vendors.
The Great American Eclipse Series
You Can Make Your Own Inexpensive High Density Filter To Photograph the Eclipse with solar filter material from Baader Planetarium
How to Tell If Your Eclipse Glasses or Handheld Solar Viewers Are Safe – the American Astronomical Society
Reputable Vendors of Solar Filters – the American Astronomical Society