Solar Filter Safety

The last couple of threads about solar filters has me wondering: how many of you out there have first hand knowledge of accidents with solar filters? I don't mean, "I know a guy who said he knew....", I mean you witnessed it. I have been observing for many years, using most means of solar filtration or projection (yeah, I even had the notorious eyepiece filter 40 years agon as a small kid)but happily have never actually seen anyone hurt their eyes with one. The worst I have personally seen: an observer who set his beard afire when he forgot to cover his finder scope. Don't get me wrong, I'd never intentionally advocate doing anything stupid, but I'm wondering how often this kind of accident really occurs.
P.S.--I'm especially interested in failure of those old eyepiece filters. I'd never use one again, even if I found one, but did anybody ever actually see one fail?

Many years ago at a far off place call college, I had a 6" relector which came with an eyepiece solar filter. The first time I used this filer I exercised caution and did not look through the eyepiece directly, about 10-20sec after getting sun light through the scope the glass filter cracked in half. I experienced no injury, just the sinking feeling that save for my cautious nature I could by one eye short.

Mike B.

That's interesting--certainly glad you weren't hurt. I'm surprised that anything other than department store refractors ever had the eyepiece filters, much less a six inch reflector. Mine was just a 60mm Tasco refractor from 1960 or so.

I witnessed a scary incident about 10 years ago which was a Finagle's Law example rather than an outright failure of a filter.

Several of us were doing solar observing and showing projected images in the midafternoon for a local elementary school at a science fair. A guy about 30 feet from me had a slip-on glass filter on the front of his refractor, which he was using for direct viewing while projecting through another scope. He was a few feet from his scope talking to a student when another kid walked by, and carelessly ran their hand along the scope tube as they passed. They managed to knock the filter off the objective end, and it hit the concrete and rolled merrily away on edge. The owner shouted a warning and took off after the filter - BUT WITHOUT MOVING THE SCOPE OFF OF THE SUN. I slapped my scope away from the the sun, tightened the axes down and started for the other scope, more to prevent anybody from looking into the eyepiece end than any other thought, but before I got there - maybe 10 to 15 seconds after the filter came off - a tiny crackling noise announced the fact that the guy had a cemented element eyepiece in the diagonal, and that it had been cracked by the suddenly expanding, outgassing cement vapor.

Lots of obvious cautions there.

Jim Mahon

P.S.--I'm especially interested in failure of those old eyepiece filters. I'd never use one again, even if I found one, but did anybody ever actually see one fail?

I doubt it, the users seeing would fail at exactly the same instant the filter would . Hmm, I guess you meant did a bystander ever see one fail.

My worries are with long term damage that is not seen for years. Solar filter saftey is based on what we think a safe level of transmission is. Only long term use would tell what the actual safe limit of transmitted UV and IR radiation is. For many this is not a concern but for other with hereditary eye conditions this might. Macular degeneration seems to be passed on from one generation to another and both UV and IR wil contribute greatly to it's manifestation in those already predisposed.

Best,
Tony Miller

Yes, this is a scary subject. I have a full aperture filter
that fits loosely over the corrector plate of my 8" SCT,
and I tape it on securely with masking tape. Also put
the lens cap on the finder scope. It's STILL scary,
especially after reading some of the reports in this
thread. Hope we all urge others to use great caution
when viewing the sun.

Well I haven't observed any failures of any filters but I have observed a accident with one, First hand!! I had a full aperture filter come off a C8. It wasn't attatched properly and a gust of wind came along and took it right off. I got quite a blast and immediately dove for the ground. I just held my eye shut for some time for fear of what I might see (or not see!!). I finally got the courage up to remove my hand and open it, everything was different shades of magenta and not near as bright as my other eye. I kept it closed for awhile more and when I re-opened it everything was differnt shades of yellow. It continually got back to normal over the next hour and I kept comparing the two to see if there was any loss. I thought all was well until I went down to the basement where it was somewhat darker, that's when I noticed that it didn't have near the same level of light gathering ability as the un-damaged one. That eventually passed over the next few hours. About 2 days after the incident my eye started getting red and irritated so another call to the eye Doctor got me a closer check up. Well after having my eye dialated for 1-1/2 weeks to help the healing the Doctor informed me that I had no pernament damage and the redness was caused by a minor scratch on the outside layer of my eye.

I take every precaution now and make sure that the filter is on very sucurely. I got lucky, extremely lucky. These are not things to casually set up. Take your time, pay attention to what you are doing, and double check everything!!.


Robert W.

The important thing isn't the filter, it's the finderscope. One can get so used to using one's telescope, that it becomes automatic - taking off the finder's cap before going outside, regardless of whether it's day or night, and looking into the finder.

Though I'd observed the sun dozens of times, one day I had a solar filter on the scope, hadn't yet found the sun, and looked through the finder for a split second before all alarms went off with a "What the hell are you doing!!!??? Why is the cover off the finder? Why are you looking into it???"

I consider myself lucky that the finder wasn't pointed directly at the sun, just in its general direction. If it came close to happening to me, it could happen to others.

I now tend to stick to using my 80mm refractor on the sun -which only has a Telrad on it.
Renato