Eclipse Safety

August 10, 2017 3:40 PM

Help me feel safe about looking at the Sun, even though I understand my hardware has been deemed safe.

I've been anticipating the August 21st eclipse viewing for 2 years. Hotel reservations for Sunday and car rental were made this past January, and I have an unobstructed viewing area on private property all ready to go. I have 3 types of eclipse glasses, as well as filter sheets to make covers for my 10x50mm binoculars. I also have a 5" Schmidt-Cassegrain telescope (currently gathering dust) which I could easily bring along, although I hadn't really considered it until now. I've never done any sun viewing before, except testing these new solar viewing glasses. The view is amazing! I literally couldn’t be more excited!

The thing is, now I'm starting to have second thoughts and even anxiety about the safety of the equipment (which is only exacerbated by all the recent "razor blades in the Halloween candy" type stories about "fake glasses flooding the market"). I checked, and they purport to be from manufacturers listed as safe on https://eclipse.aas.org/resources/solar-filters and show the correct ISO numbers.

So, my question is/are, how do I know that this equipment is safe? Can I test it myself? Also, am I correct that, if the filter sheets are safe, that I can simply cover the objective lenses of the binoculars, and voila, they're now safe to stare at the Sun with? And the same for the 5"? Honestly, the thought of using either the binoculars or telescope at this point is just freaking me out.

Any insights would be appreciated.

I got the following from Amazon months ago:

Eclipser HD Safe Solar Plastic Viewer
Celestron 4 pack Observing Kit
8"x8" Solar Filter Sheet
Green Shade 14 Solar Eclipse Glasses (Amazon is showing 404 now for these?)

*bonus question: I understand that it's safe to look at the totality without protection, but can I look at it with my binoculars? (assume I never look outside of the totality)

posted by Pig Tail Orchestra to Science & Nature (7 answers total)

I got my eclipse glasses and literally walked outside and looked at the sun. They are really really dark. Like the sun was dim and boring; I assume that's a good thing. You could go test them right now. Everyone has briefly looked at the sun with regular sunglasses and survived. You seem to have done lots of due diligence regarding the lenses in your glasses.

My understanding is that you should never look at the sun through magnified optics unless there is a manufacturer approved filter at the front of the lens that is specifically engineered for sun viewing. I would be really cautious to try a homebrew method of putting the sheeting in front of binoculars or telescope.

Perhaps invest some time in a making a simple "camera obscura" rig with your binocs and filter sheets.
posted by TomFoolery at 4:29 PM on August 10, 2017 [6 favorites]

Best answer: I like the camera obscura method, and might try it. (Did this for the transit of Venus.)

I intend to use the same 8x8 sheet to construct "homebrew" objective filters for large binoculars. The makers of such films endorse this.

It is essential, if you take your filters off the binoculars to look at the corona briefly (which you probably want to do), that they be put back on before totality ends (or the binoculars be capped and put away).

I recommend not taking the 5" Schmidt-Cassegrain, since (1) what you could usefully do with it in the ~2 minutes of totality is rather specialized, and requires preparation and experience using the telescope (e.g. tracking the sun); (2) this detracts/distracts from looking around at earth and sky; and (3) binoculars are adequate for most needs.

I have a long-idle 4.7" f/8.3 refractor that will stay at home, though trying to take photographs might be fun. I've been unable to prepare, test or dry-run anything, so I leave that to others. I don't want fussing with a telescope to ruin my experience; if totality lasted 2 hours(!) I would argue differently. There will be millions of bad eclipse snapshots -- and hundreds of good photographs to show us what the close-ups looked like.
posted by lathrop at 5:28 PM on August 10, 2017

Check your product/vendor against the following list provided by the American Astronomical Society.
posted by Napoleonic Terrier at 6:11 PM on August 10, 2017

You shouldn't be able to see anything through eclipse glasses except the Sun, and that should be comfortable to look at.
posted by monotreme at 8:38 PM on August 10, 2017

Best answer: The only other thing I would mention is that you should check your sheets for holes or scratches before you look at the sun, especially if you're using the with a telescope or binoculars. You can hold them up to a bright light source (not the sun) to check to see if you see any pinholes or lines. If you can then don't use that sheet/glasses.
posted by runcibleshaw at 11:06 AM on August 11, 2017

Response by poster: Thanks for all the great suggestions. I rechecked my list of vendors, tested my binoculars as a camera obscura, and am finishing creating filters as shown by by lathrop's suggestion.

I did test my glasses and filters by looking directly at the sun for varying amounts of time... I don't notice any lingering palinopsia, so I guess that should suffice?

Does anyone have a link showing that it's ok to look at the total eclipse with unfiltered binoculars?
posted by Pig Tail Orchestra at 5:10 PM on August 14, 2017

Best answer: According to this Forbes article, it's safe to observe the eclipse during totality with a telescope or binoculars. However, be keenly aware of how long totality lasts in your location and stop using such devices a safe period of time before totality ends -- even a brief glimpse of raw, magnified sunlight can cause serious damage to your eyes.
posted by Rhaomi at 8:47 PM on August 16, 2017