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Use of vintage eyepiece sun filters.

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#76 Jon Marinello

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Posted 03 June 2011 - 12:12 PM

Here is a shot of the Star Diagonal I am using for this test. It has an EP barrel (nose) instead of the stock barrel so that I could screw the sun filter into the nose for this test.

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#77 Jon Marinello

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Posted 03 June 2011 - 12:30 PM

I have an important update to test 2, 60mm. The filter did crack! I was looking over the filter this morning and it has a small hairline spider crack that I missed yesterday! :foreheadslap: Remember this was the test where the sun filter was screwed into the eyepiece. Note that the filter did not shatter or break in pieces. Unlike when I used on in the 102mm when it broke in two but did not shatter.

This is probably the best result we could hope for in a way. In at least one case (this one), the filter cracked when used per the manufacturer's instructions! And that was in a 60mm scope. That said the filter is really old but that's what we have to use and test these days.

It's looking like the data is pointing in a clear direction although not statistically significant.

If anyone has any extra sun filters that would help me here. I only have a couple left and I want to repeat some of the experiments. So if you can send me one or two please PM me. I will return any unused filters.

I have included a shot using my Canon PowerShot SD400 (Elf) looking directly through the cracked filter. This is the best shot I could get of the crack. It is extremely fine but you can see the visual anomaly it causes in the picture.

Thanks!

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#78 Jon Marinello

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Posted 03 June 2011 - 12:32 PM

Here is a shot of the sun filters sacrificed so far.

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#79 Jon Marinello

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Posted 03 June 2011 - 12:35 PM

Note that in this test, my sun filter's lock ring is a bit corroded and I can't get it to loosen up a bit. That might cause it to crack faster then if it was loose due to heat expansion.

#80 Joe Cepleur

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Posted 03 June 2011 - 03:00 PM

Note that in this test, my sun filter's lock ring is a bit corroded and I can't get it to loosen up a bit. That might cause it to crack faster then if it was loose due to heat expansion.


Great detail. In the real world, the quality of any given sun filter is unknown. Your noting flaws helps to show the kinds of breakages that could occur if people made the mistake of extrapolating theoretical opinions about safety into their own observing.

Neat to have already shown that even with 60mm objectives, these filters are not reliable, even if it is not yet clear how often the failures are hairline versus catastrophic (nor ever may be, with the limited number of filters available). Are you 100% sure the crack did not exist prior to your starting the test?

#81 Jon Marinello

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Posted 03 June 2011 - 03:18 PM

Yes I'm completely sure.

#82 Jon Marinello

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Posted 03 June 2011 - 03:20 PM

Unfortunately, the weather didn't cooperate today. High clouds rolled in shortly after the test began. I am going out of town for the weekend so the tests will have to wait until next week.

#83 strdst

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Posted 04 June 2011 - 05:13 PM

Case History #3745 or whatev.

Actually being a survivor of two glass sun filter failures while observing I thought I should chime in.

In 1966 in SoCal probably in February, maybe March, while looking into the soul of Sol the screw in sun filter snapped big time exposing me to a "blinded by the light" experience. I was 14 and using a Tasco 11 te 4.5" reflector. This was a scope that I only had for a few months while I was visiting the "dark side" of reflectors and soon came back to a 3" Edmund refractor. The Tasco sold for $89 and would have been da bomb except there was a collimation or secondary mirror issue. Anyway there was an offset opening as I recall in the tube cap. This was to reduce the amount of light for solar observing. I know that now but then... I was much too smart to read the instruction manual :lol: I can't say if I was viewing with reduced aperture but in any event the filter snapped leaving a pretty wide gap and a momentary exposure to unfiltered sunshine. I experienced a few minutes of panic and darkness in the exposed (left) eye. Eventually things became "normal". I can still feel the heat generated in that moment.

Being a big fan of the sun which was in a pretty intense sunspot stage I was more disappointed that the filter broke than anything else. Anyway because the Tasco 11 te never could be collimated to specs. (less than four images of Jupiter in the ep at any one time) the owner of "Optech Precision Instruments" (I bet Lew knew this gentleman) offered a deal on an Edmund 3" refractor as a upgrade/substitute. I believe the Edmund was $125 at that time and I'm quite sure we paid somewhat less. The Edmund used 1.25 ep's and I recall digging deep to purchase a solar filter with a rubber cup that fit over a 1.25" ep like a eyeguard. I was told this wouldn't break like the other kind. It must have cost a lot then... like $2.50. I used this for zillions of hours with the Edmund scope. I was hooked on sunspots and granulation and didn't let a day go by for the next few years without taking a good look at the sun. I never had a failure with this filter.

In 1995 or so I picked up an old orange C-8. I was surprised that when looking at bright objects like Jupiter or Saturn my left eye (eye for observing) gave me a mellow view and my right eye was overwhelmed by brightness unable to discern much detail. It was like my left eye was looking through a ND filter. I remembered the Tasco experience. I believe that that burst of light affected some rods for sure. The difference between what my eyes can see as far as magnitude is apparent. I don't notice this except in the eyepiece. Of course my left (primary) eye is the one that talks to what's left of my brain... I do need it!

And knowing that sun filters break but being quite risk tolerant I recently was observing sun spots once again with a 60 mm scope when the screw in filter snapped. The split was minimal the light was very bright but nothing like the first exposure back in the 1960's. I don't believe this second exposure has contributed to the dimming down of my left eye. I do like the filtered view, the orange/yellow/green (whatever) that they provide. Projection isn't really viewing for me so I don't use that technique. I actually have a device that came with an old Goto telescope that can project a solar image onto a wall for a classroom of students to see. I haven't tried it yet.

The Goto Kogaku and Nippon Kogaku scopes that I have came with solar filters that cover the eyepiece like the one that I bought for the Edmund 3". Even though the filter glass is right there at your eye surface (being on top of the ep) I don't think it absorbs much heat. The Goto Kogaku even came with a Herschel wedge/ star diagonal for sun viewing. If it ever clears here I'll try it out.

Here are some pics of how the Nippon Kogaku filters attach to ep's. They might be safer but as metioned before a full aperture filter is the best way to go.

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#84 strdst

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Posted 04 June 2011 - 05:16 PM

ep cap removes without affecting lenses

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#85 strdst

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Posted 04 June 2011 - 05:49 PM

The ep ready with filter attached.

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#86 Jon Marinello

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Posted 04 June 2011 - 07:16 PM

Thanks for adding this type of filter to the mix. I had forgotten about these.

Unitron made a similar over the top of the EP filter for both solar and lunar versions. I have a pair of them. Does anyone else have experience with this type of solar EP filter?

#87 Joe Cepleur

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Posted 05 June 2011 - 08:03 PM

All things being equal (glass of fhe same composition, thickness, and tint), filters fitting over the end of the eyepiece should be less likely to break than those fitting inside the barrel. Because they fit as far as possible from the focal point, heat would be less concentrated. Even so, it would still be better to filter the entire objective.

#88 Steve_M_M

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Posted 05 June 2011 - 10:30 PM

Jon, if you run out and your eyes survive, I have a bunch of spares for you :)

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#89 strdst

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Posted 05 June 2011 - 10:48 PM

I have a few as well but Jon can't have them. I'm thinking checkers or solar filter bingo markers...

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#90 Jon Marinello

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Posted 05 June 2011 - 11:32 PM

Hey Steve,

Send them on over. I can definitely use more for this experiment. I believe you have my address.

Thanks!

jon

#91 Jon Marinello

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Posted 05 June 2011 - 11:33 PM

That was cold! :lol:

#92 DarkSkys

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Posted 05 June 2011 - 11:38 PM

So are these filters the same type of stuff as a No/14 welders filter?

#93 Joe Cepleur

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Posted 06 June 2011 - 06:56 AM

I want to see this experiment continue so that this longstanding issue can finally be settled. More data, and more firsthand stories, would only solidify the emerging picture: these filters can indeed break when used, and although the result is not necessarily instant blindness, we have strdst's report of instantly, permanently altered vision. Clearly the engineering is inferior, in that the design places the filter at or near the the most intense concentration of heat. With better alternatives, none of which permanently alter one's classic scope, these old filters should not be used.

#94 BigC

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Posted 06 June 2011 - 10:14 AM

Welding filters have been recommended as safe for eclipse viewing,and even for regular solar viewing if large enough to cover the objectives of a binocular.Or use one welder glass on each binocular objective.Just don't forget that the binoculars or telescope gathers more sunlight due to the bigger aperature so instead of the 2mm daylight pupil's area the sunlight from a 35,60mm or whatever lens is being concentrated and beamed into the eyeball.
Since blindness is a serious handicap to observing,I would always err on the side of caution.
Looking through some old filters that are KNOWN to be risky just seems ,well, foolish!Use a full aperature filter of proven safe design and preserve your eyesight.

#95 BigC

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Posted 06 June 2011 - 10:27 AM

Since the little eyepiece sun filters "color" the view anyway,I propse a welding glass large enough to completely cover the objective as a minimum safety precaution if anyone insists on trying to use the old "sun" filters.Welder's filters are available in 4x2 and 4x4 as I recall,although it has been a long time since I last struck an arc.One of the #12 welder's filters might work well as a full-aperature filter WHEN USED WITH the old eyepiece filter.The even darker #14 is recommended elsewhere for direct viewing when it is the only filter used in low magnification optics.
Please understand these are a layman's opinions ,not advice, and you do any such experiments entirely at your own risk.

#96 Joe Cepleur

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Posted 06 June 2011 - 10:58 PM

Welding filters... interesting possibility. How bright is the Sun, compared with the flame or arc of a weld? Welding is done at no magnification, whereas a telescope concentrates lots of light from a large objective and passes it through a small eyepiece. The welding glass thus may look virtually opaque to the naked eye, perhaps even be comfortable when held blocking the Sun for the naked eye, and yet not be dark enough for viewing the Sun through a telescope. Anyone know for sure? At least we are on the right track, if we are covering the objective.

#97 Steve_M_M

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Posted 08 June 2011 - 09:16 PM

Does anyone know how one of these solar filters compares to an ND 3 filter?

Steve

#98 DAVIDG

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Posted 08 June 2011 - 09:35 PM

Does anyone know how one of these solar filters compares to an ND 3 filter?

Steve


A ND-3 filter reduces the light by 10^3 or 1000:1. For safe solar viewing you need 100,000:1 or a total of ND-5.
Welder's glass Shade numbers is SN = 1 + (7/3)*OD were OD is the optical density. Welders glass #14 works out to optical density of 5.57 or over 100,000:1 in the reduction of intensity.
The eyepiece Sun filters should be at least ND-5.

- Dave

#99 k2power

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Posted 08 June 2011 - 09:43 PM

I recall using one as a teenager with my Jason 76mm tabletop. I never let the scope stay pointed at the sun for more than a few seconds before pointing it away. I was always cautious about the potential for breakage and never had one break. Granted, I didn't use one often but was able to see my first sunspots with them. Never used them on any other scope.

#100 Steve_M_M

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Posted 08 June 2011 - 09:56 PM

Dave,

Thank you. That is what I am looking for. So, a "sun" filter with a herschel wedge should be more than ok, right? Maybe actually too much blocking?

Steve


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