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Equipment Discussions >> Classic Telescopes

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Bob Myler
Carpal Tunnel
*****

Reged: 05/18/06

Loc: St Louis, MO
Re: Use of vintage eyepiece sun filters. new [Re: Jason H.]
      #4866671 - 10/17/11 09:07 PM

OK. I won't. I promise.

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Jason H.
Pooh-Bah


Reged: 11/23/07

Loc: Central Florida
Re: Use of vintage eyepiece sun filters. new [Re: Bob Myler]
      #4868623 - 10/18/11 11:02 PM

Quote:

OK. I won't. I promise.




Not you! That's just a legal disclaimer.

Jason H.


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sftonkin
sage
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Reged: 02/25/04

Loc: W. Hampshire , UK
Re: Use of vintage eyepiece sun filters. new [Re: Jason H.]
      #4879241 - 10/25/11 10:47 AM

In case its of interest, I videoed the "testing" of one of these filters earlier this year; I put the result on YouTube:
http://www.youtube.com/watch?v=G5xb3b-vRd4


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Bob Myler
Carpal Tunnel
*****

Reged: 05/18/06

Loc: St Louis, MO
Re: Use of vintage eyepiece sun filters. new [Re: sftonkin]
      #4880270 - 10/25/11 09:17 PM

Impressive realtime demonstration. The flash is instantaneous - and our reflexes far too slow.

The damage is done before the blink is completed.


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greju
Carpal Tunnel
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Reged: 10/13/05

Re: Use of vintage eyepiece sun filters. new [Re: sftonkin]
      #4880297 - 10/25/11 09:32 PM

Quote:

In case its of interest, I videoed the "testing" of one of these filters earlier this year; I put the result on YouTube:
http://www.youtube.com/watch?v=G5xb3b-vRd4





Good for you! It is nice to see a post in this thread that definitively states NOT to use these filters. Unlike the title of the thread and the many posts that I took to say that it was ok to use some filters some of the time. Hopefully no eyes will be ruined because someone just saw the title of this thread and did not read thru all the pages before getting to your post which shows in no uncertain terms that eyepiece sun filters should never be used. Thanks for your video.


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MacScope
sage
*****

Reged: 12/18/04

Loc: Western Pennsylvania USA
Re: Use of vintage eyepiece sun filters. new [Re: greju]
      #4881062 - 10/26/11 10:21 AM

Now to play devils advocate: the solar filter instructions I have seen state they are not for use with an objective over 60mm or as in my 80mm Vixen there is a lens cap to stop down the objective to 50 or 60mm. The above test is with a much larger objective lens I believe. NOTE: I am NOT advocating use of these filters!

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Joe Cepleur
Carpal Tunnel


Reged: 03/18/10

Loc: Dark North Woods
Re: Use of vintage eyepiece sun filters. new [Re: MacScope]
      #4881239 - 10/26/11 11:48 AM

It's true that these solar filters were intended for 60mm apertures and smaller, and also obvious that, it one wants to film a crack appearing, using a larger aperture makes a somewhat random process predictable. The anecdotal evidence we have gathered collectively ranges from tales of people using these filters for many years without problems, to stories of partial loss of vision from sudden failure. Reports include failures when used with proper aperture.

The bottom line is that these filters are of questionable quality, to due both their considerable age and the uncertainty about the quality control and engineering involved in the manufacturing of any particular example so many years ago. From an engineering point of view, filtering at a focused area of concentrated heat is crazy, at least without proper means to vent the heat, as in a Herschel wedge. There are far better alternatives, including filtering at the aperture, where the heat is diffuse.

Anyone who wants to use these filters in conjunction with cameras, go ahead. Worst happens is you destroy some cameras. Using them with the only two eyes you'll ever have is foolish. We need to take a stand and say so. By continuing to question this issue, we endanger the welfare of the many people who turn to these forums for authoritative advice.

It's past time to re-title this thread. Is there a way to change it from:

Use of vintage eyepiece sun filters

to:

Dangers of Vintage Eyepiece Sun Filters


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sftonkin
sage
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Reged: 02/25/04

Loc: W. Hampshire , UK
Re: Use of vintage eyepiece sun filters. new [Re: MacScope]
      #4891377 - 11/01/11 02:32 AM

Quote:

Now to play devils advocate: the solar filter instructions I have seen state they are not for use with an objective over 60mm




I have been encountering these things for about 40 years. I do not recall ever having seen that warning on any of them.

Quote:

The above test is with a much larger objective lens I believe.




Yes, it is. A few reasons for that:
  • It's the only scope I have that is suitable for solar use without a "big end" filter.
  • I wanted the filter to fail before the camera battery ran out.


However, that said, I have, before the days of digital video, tested these things to destruction with 60mm refractors. Needs a high Sun, transparent sky, and a lot more time.

On a related note, there is a lot of incorrect knee-jerk stuff written about solar safety and it is almost inevitable that thinking people will realise that some of it just doesn't make sense so will ignore it -- that is a dangerous situation. I believe that it arises largely because most people do not recognise that there are at least three distinct mechanisms for solar eye damage. For example, most people will realise that there is insufficient heat coming through a pinhole in eclipse shades to "fry" the retina, but are probably ignorant of photochemical retinopathy, which is the mechanism for damage from the pinhole.

The only safe "short form" advice is "DON'T RISK IT", but unless we explain why correctly in the "long form", we risk having people ignore the "short form" -- that way lies potential eye damage.


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Spectral Joe
super member


Reged: 02/28/11

Loc: Livermore CA
Re: Use of vintage eyepiece sun filters. new [Re: sftonkin]
      #4936475 - 11/26/11 10:14 PM

OK, I have to admit first that I haven't taken the time to read the whole thread, so bear with me if I'm repeating anything. First, I'm with those that say that these filters should be avoided at all cost. Pack it away as an artifact and use either a Herschel wedge or a modern full aperture filter. Second, with regard to these being "safe" with smaller apertures, remember that these are located very close to (or at) the exit pupil, which is an image of the objective. The power density at this point is the highest, and power density goes up as the inverse of the square of the pupil size. Doubling the magnification will raise the power density by a factor of four. The increased power density in a smaller area will make the temperature gradient across the filter steeper, and this gradient is what cracks the filter. Thus, stating that the filter is safe for a given aperture must be accompanied by what eyepiece designs and focal lengths can be used with the filter at that aperture. It's a lot easier to just use what is known to be safe.

Joe


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wfj
Pooh-Bah
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Reged: 01/10/08

Loc: California, Santa Cruz County
Re: Use of vintage eyepiece sun filters. new [Re: Spectral Joe]
      #5256928 - 06/05/12 09:36 PM

There's one more safe use. I just held a vintage eyepiece solar filter up to my eye (no telescope) to see the Venus transit - works like a charm!

Perhaps they'd fine ... on the objective end of a telescope !


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greju
Carpal Tunnel
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Reged: 10/13/05

Re: Use of vintage eyepiece sun filters. new [Re: wfj]
      #5256972 - 06/05/12 10:09 PM

Quote:

There's one more safe use. I just held a vintage eyepiece solar filter up to my eye (no telescope) to see the Venus transit - works like a charm!

Perhaps they'd fine ... on the objective end of a telescope !




Not only a bad idea but you certainly would not see the transit unless you also had bionic eyes!


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wfj
Pooh-Bah
*****

Reged: 01/10/08

Loc: California, Santa Cruz County
Re: Use of vintage eyepiece sun filters. new [Re: greju]
      #5264818 - 06/10/12 02:17 PM

Wrong. I did it, and saw Venus quite easily as a disc.

Made an impact on me - I wondered if instead if Venus had been in resonance with Earth's orbit, so that Venus transits were more of a common case, then when total solar eclipses would occur, you'd tend to see a nearby planet in the sky as a naked eye disc, how we might have had a faster appreciation of the laws of gravitation prior to telescopes.

Venus was almost a minute of arc, while the sun was less than 32 minutes. Most people can make out lunar features naked eye that are a fraction of its diameter.

Doesn't take bionic eyes - duhhh. Such a joy CN senior members can be ...


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Brian RisleyModerator
Carpal Tunnel
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Reged: 09/04/06

Loc: SW Florida
Re: Use of vintage eyepiece sun filters. new [Re: wfj]
      #5264902 - 06/10/12 03:20 PM

Guys, remember the TOS. Be Polite!

As to being able to see it with just a filter, I think that people were able to see it with the solar glasses/viewers, which would be the same as looking through an eyepiece filter hand held. It was large enough to be detectable with many standard cameras, so I suspect it was visible.
Brian


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greju
Carpal Tunnel
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Reged: 10/13/05

Re: Use of vintage eyepiece sun filters. new [Re: Brian Risley]
      #5265393 - 06/10/12 10:04 PM

Since you are going to let these statemends stand I will happily respond to them.

"Doesn't take bionic eyes - duhhh. Such a joy CN senior members can be ... "

You seem to think you know my age. So what is it? And what would age have to do with it?

I will again say that holding up a small eyepiece sun filter to your eye is a bad idea, duh! It is also not a lens, you could not see the transit. And to say on a public forum that "There is one more safe use" is irresponsible at best. Looking at the sun in this manner is not "safe", no matter what age you are. Duh!

"As to being able to see it with just a filter, I think that people were able to see it with the solar glasses/viewers, which would be the same as looking through an eyepiece filter hand held."

You "think" this? And comparing "solar glasses/viewers" to a vintage eyepiece sun filter are not the same and by you seemingly condoning this are you saying this is a "safe" practice also? Oh, and cameras have lenses. I suspect that might have helped. I bet those cameras were equipped with a proper solar filter also. Not someone holding a vintage eyepiece sun filter up to the lens.


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Rich (RLTYS)Moderator
Postmaster
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Reged: 12/18/04

Loc: New York (Long Island)
Re: Use of vintage eyepiece sun filters. new [Re: greju]
      #5265761 - 06/11/12 05:56 AM

Come on folks lets keep this important discussion friendly.

Rich (RLTYS)


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Joe Cepleur
Carpal Tunnel


Reged: 03/18/10

Loc: Dark North Woods
Re: Use of vintage eyepiece sun filters. new [Re: Rich (RLTYS)]
      #5265864 - 06/11/12 08:33 AM

If one wanted to use a tiny eyepiece filter to look at the Sun directly, it would be safer to mount it securely behind a larger mask. Better, if one slips with one's hand, to have one's vision blocked by the mask, than to suddenly allow the Sun's rays to strike one's eye. No one has ever reported such a filter cracking due to direct exposure to the Sun (without an objective lens concentrating the Sun's rays from a larger area). Still, I would not want to advocate this use of antique filters, because it confuses the otherwise clear message not to use filters of unknown and questionable quality. That said, to play fair, at least in this case, the method clearly worked. No eyes were fried, and the experimenter unsurprisingly reports having seen the transit.

I spent $40 with shipping on a brand-new sheet of modern solar viewing film that allowed me to safely filter, at the aperture, two binoculars and a refractor -- an excellent investment for a once-in-a-lifetime transit! There was enough film left over to filter several other instruments. A club could share a sheet at a cost of five to ten dollars per person.

It's sad that the fury has obscured the comment that our sense of gravitation and celestial mechanics could have arrived much earlier in our history if Venus had a different orbit, making it visible during eclipses. That's profound.

I'll second the call for good manners. On the occasions when I have been first to make the request, I've wished others would join me.


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wfj
Pooh-Bah
*****

Reged: 01/10/08

Loc: California, Santa Cruz County
Re: Use of vintage eyepiece sun filters. new [Re: Joe Cepleur]
      #5268050 - 06/12/12 12:50 PM

Digression.

Did this on a lark as I was hunting through an eyepiece bin, setting up a scope for some to see transit using eyepiece projection. Came across one from a flea market, and I noticed then it had a sun filter on it. I pick these up routinely for a buck or so, and often don't look too closely.

So I wondered, what the heck, why not check it out naked eye, as the optical density of these things are around 60. Naked eye sunspots I'd seen at sunset before.

And I wasn't knocking age, I was referring to "senior" as in large number of posts.

I remember when members of a local astronomy group were experimenting with high mag / tiny exit pupils on full aperture solar filters and comparing what they saw with pinhole projection. They were experimenting with geometric optics of a sort. Some of longer term members of the group decided this was "wrong", analogizing to the department store scopes high power thing, that they were doing a disservice to astronomy, and tried to ridicule them out of the group. Some acted as stalkers, to "police" thought as well.

Happens to lots of communities. Online as well.


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JonH
sage
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Reged: 04/07/12

Loc: Brisbane Australia
Re: Use of vintage eyepiece sun filters. [Re: wfj]
      #5446383 - 09/29/12 08:28 AM

Perhaps the heat in this debate is a useful and important thing.......I came to astronomy quite by chance having purchased a brass victorian parlour telescope as an object d'art. This came with three eyepieces, terestrial;astronomical and a mysterious "smoked" objective. Naturally I assumed this was for solar observation and promptly set up the scope to look for sun spots. Bearing in mind I did this in the height of summer, in Australia, with a sunglass that could have been a centuary and a half old, I was fortunate not to lose the sight in one of my eyes. Later, whilst looking for a larger tripod I came across Cloudy nights and this debate and realised the danger inherent in the beautiful brass tube work. I have kept the sunglass, but it is carefully labelled to alert any other casual viewers to its dangers. I wonder if I had'nt read this thread with its "heated" debate and occasional spots of rancour, weather I might not have experienced a moment of innattention and tried the sunglass again? I love Cloudy nights for the maturity of its correspondents but I also love it because its members are not afraid to make a noise about stuff that matters. Incidentaly, I had the brass scope out for this year's transit, stopped down and set for solar projection together with my Unitron.

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dgreyson
scholastic sledgehammer
*****

Reged: 11/06/12

Loc: South Carolina
Re: Use of vintage eyepiece sun filters. new [Re: JonH]
      #5560064 - 12/07/12 10:21 PM

I used to use the solar projection plate on my 60mm tasco 7te to look at sunspots back in the day when I first got it. they looked pretty cool so I took off the plate and screwed the glass sun filter into an eyepiece. Took a look and it was much better, the granularity of the spots was very interesting. I looked up for a moment to check where and what my brother was doing (he had a nasty habit of throwing rocks, broke my giant ant farm once ).

I had looked away for only a moment or so and when I turned back, before I could look again, the filter had cracked wide open. Dag! Cheap J*p junk I thought and threw the broken filter away and never looked at the sun again.

I was lucky, I could have easily been blinded. never realized that until I read this post and remembered the occasion. woagh!


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bouffetout
scholastic sledgehammer


Reged: 11/21/12

Loc: Canada
Re: Use of vintage eyepiece sun filters. new [Re: dgreyson]
      #5603244 - 01/03/13 03:32 PM

I had one on my 4.25" newton ,years ago...I sat down for a break ,and the solar eyepiece shattered and little pieces of glass flew off the filter. Most of the filter was still there but cracked like I would with a hammer !
Have I stayed there watching the sun for longer,those pieces of glass would have ended in my eye...


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