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Use of vintage eyepiece sun filters.

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#176 Joe Cepleur

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Posted 11 June 2012 - 07:33 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.

#177 wfj

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Posted 12 June 2012 - 11:50 AM

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.

#178 JonH

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Posted 29 September 2012 - 07:28 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.

#179 dgreyson

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Posted 07 December 2012 - 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!

#180 bouffetout

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Posted 03 January 2013 - 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...

#181 photiost

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Posted 06 January 2013 - 03:50 PM

With so many safe and inexpensive Glass and Mylar Solar filters available today why take ANY chance with these on your eyesight?
The BAADER AstroSolar film is my personal favorite.

If you want to observe Sunspots and have no "Safe" filter available, then eyepiece projection
(solar image projected onto a white paper) is really the only safe alternative.
.

#182 Jean Mario

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Posted 04 April 2013 - 06:51 PM

is good for long time...

#183 Jean Mario

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Posted 05 April 2013 - 03:15 PM

I have the BAADER filter it's the best a good for long time...

#184 Chris Lord

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Posted 19 April 2013 - 05:30 AM

Realise it's been a while since this thread was active, but I thought you may all like to know I've uploaded an article on this subject to my website's <FORUM> page (forum in the sense that the articles are open market and can be used by anyone gratis).

Forum article <#31> desrcibes the historical aspect to sun eyecap filters, rather than their more modern (relatively speaking) TASCO etal counterparts.

Sun eyecap filters, or "solar shades" as they were originally described, were fitted to Dollond and Ramsden refractor eyepieces (usually Huyghenians), and later Ramsden's successor Matthew Berge. They comprised a brass screw on cell with a red dyed in the mass glass filter spun tightly into the cell leaving no room for expansion. This same design was made by various refractor makers throughout the C19th and well into the C20th. I have many in my collection, made by Wray, Broadhurst Clarkson & Co. Cooke, Troughton & Simms & Ottway. They are all identical in having a 1".348 x 28TPI Whitworth screw thread. Grubb also made the same type of solar shade which was a tight push fit.

At the time nothing was known of retinal scotoma <http://en.wikipedia....g/wiki/Scotoma> caused by IR leakage. In fact William Herschel had only just discovered infra-red radiation at the turn of the C19th. The metalic gold colouring agent absorbed from blue thru' near red, but allowed deep red and infra-red thru'. They give a dull red image not because there is little light passing thru' but because there is little blue thru' near red transmitted. The eye can't see near IR, and about 2% of the deep red gets thru' presenting a deceptively comfortable image because the eye is quite insensitive to deep red light. Little IR is absorbed, so even if the filter doesn't fail it can cause retinal scotoma.

I also realise the 1950's thru' early 70's TASCO sun filters used #14 welder's type glass, giving a green-yellow image. These are slightly different in their optical properties viz a vis the retina, but nonetheless are potentially very dangerous.

The forum article describes a spreadsheet model I have created to investigate the time before failure of antique solar eyecap filters. If having read the article (a downloadable pdf) you would like the spreadsheet to play around with yourself, and if you use an Apple Mac running Appleworks, just e-mail me.

I have only ever used one of these red solar shades on a 5 draw hand held 2-inch refractor on the setting sun, for a few minutes. If you'll accept my advice, and you have a sun eyecap filter amongst your accessories, please don't be tempted to use it. It simply isn't worth the risk.

article is:
<http://www.brayebroo...SUN FILTER.pdf>
e-mail address for spreadsheet:
<chrislord@brayebrook.demon.co.uk>

#185 Jon Marinello

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Posted 21 July 2013 - 06:16 AM

Nice to see this topic is still alive and well.

jon

#186 mikey cee

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Posted 21 July 2013 - 10:16 AM

Nice to see you are as well! :shocked: :lol: :lol: Mike

#187 brianb11213

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Posted 11 August 2013 - 05:44 AM

With so many safe and inexpensive Glass and Mylar Solar filters available today why take ANY chance with these on your eyesight?
The BAADER AstroSolar film is my personal favorite.

Indeed.

If you want to observe Sunspots and have no "Safe" filter available, then eyepiece projection
(solar image projected onto a white paper) is really the only safe alternative.
.

Safe for your eyes but not for your scope.

The concentrated solar heat can and will melt the cement in modern eyepieces. If you're using vintage eyepieces (Huyhenian or Ramsden) you'll get away with it but orthos, plossls and modern multi-element eyepieces will be rapidly damaged or destroyed if used for solar projection.

Solar projection is for use with small refractors only. The concentrated heat will damage secondary mirrors and/or their fittings and/or plastic baffles used in reflecting telescopes of all designs. Even with small refractors, it's probably best to avoid projection with modern scopes, as they may well have plastic baffles which will melt or burn if the sun strikes them whilst you're trying to centre it.

#188 checksum

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Posted 28 August 2013 - 12:57 PM

Personally I would not risk my eye sight with such things and would strongly encourage you all to do the same.

Clear skies, not blind eyes!

#189 Lindberg

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Posted 25 November 2013 - 04:13 PM

I made this for my 75 mm Refractor

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#190 Lindberg

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Posted 25 November 2013 - 04:14 PM

And here it is I never trust a small 0.95 or 1.25" solar filter

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#191 Joe Cepleur

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Posted 06 December 2013 - 06:10 PM

Personally I would not risk my eye sight with such things and would strongly encourage you all to do the same.

Clear skies, not blind eyes!


To which "such things" does this refer? Baader solar film? The similar film from Thousand Oaks Optical? While I, too, an nervous about anything that increases the heat inside my scope, filtering at the objective is safe if done correctly. Light that never enters our scopes can't hurt us. One must always assure that the film is in perfect condition and securely attached, and that finders as well as main scopes are filtered.

Viewing the Sun is fascinating. While everyone who tries it must accept responsibility for proper use of solar viewing gear, I am against broadly discouraging this branch of astronomy. I built my first solar filter from Thousand Oaks film for the Transit of Venus, and I'm glad I did!

It is specifically filtering concentrated light at the eyepiece that this thread discourages.

#192 oldmanastro

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Posted 12 December 2013 - 09:59 PM

I used these filters back in the 60s with both my 76mm and 60mm Sears Scopes. Never stopped down the aperture and never had a cracked filter. I used to draw sunspot groups and this took sometime at the telescope. Good luck was with me those days. I don't use them anymore although sometimes i get this urge to use them for old times sake. Just a peek.....

Guido

#193 Karl Fabian

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Posted 05 January 2014 - 04:21 PM

I do not recommend using these. Most likely the reason some have been lucky with these filters is that when used with a longer focal length Huygens eyepiece the focal plane (where it is hottest) is often forward of the filter where it is not quite as hot, but still dangerous. The focal plane of a Huygens ocular is between the two lenses that make up the eyepiece. In a longer .965 focal length Huygens this would typically be about an inch from the filter when the image is in focus. On these filters the filter glass should RATTLE in the holder and not be tight to allow for expansion. I have seen many that were tightly fit in the holder. THOSE ARE ALMOST GUARANTEED TO FRACTURE! Not a good idea to use these,even the ones that rattle, especially with very affordable full aperture filters available. Anything near the focal plane has the potential to overheat. A filter over the aperture of the scope is the way to go.

#194 Mike E.

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Posted 21 February 2014 - 10:33 AM

Here is an excerpt from a 105 year old Amateur Astronomy book about observing the Sun. It's interesting that danger of cracked eyepiece filters were well known back in 1909, and the alternate method of projection suggested; yet Telescscope manufacturers continued to provide these filters for at least another 70 or more years.

:ohmy:

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#195 SeeEmComing

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Posted 23 March 2014 - 01:37 AM

Hey Dave,

I really like your 4.25" f/10 Solar Newt, with the
herscell wedge I will download the picture and
study it more closely, Great Job! Nice work!
Here is my 3 1/2" Antique Reflector which I
restored to its original appearance

SeeEmComing :jump:

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#196 Balok

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Posted 26 September 2014 - 09:54 AM

I would not view the sun with any questionable filters when  safe options exist: the retinas have no pain receptors, we cannot feel the damage happen and  it may

 

take time, even years, to develop symptoms. The eyelid and other optical structures are thin - easily penetrated by light and UV light.

 

We have but one set of eyes. Protect them.

 

If one feels nostalgic ; the pinhole sun screen projection method and  external Mylar filter cap are safe options.

 

The Classic Telescope Police won't arrest you for that.

 

Best  keep the opthamologist on call when using iffy solar viewing filters. 

 

I would not want any of you to risk eye damage for nostalgia.

 

 

That's my 2 zulaks worth.

 

Regards,

 

Balok



#197 BigC

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Posted 28 September 2014 - 08:48 AM

Mike E.

 

A recent  eyepiece purchase included a surprise: a 1.25" SUN filter similar to those  included with classic scopes in the .96 size for all those years.Had not known this  type was made in the more modern size.



#198 dawziecat

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Posted 29 September 2014 - 09:46 AM

I know this horse has been flogged to death, but . . .

 

In the very early 1960's I had a Polarex 4" eq. It came with an eyepiece solar filter and a "dust cap with a hole in it" aperture stop down.

It cracked.

I  ordered a replacement from Unitron. It cracked too.

 

Can't say as I appreciated the danger . . . but recognized these things were gonn'a crack. I did not try a third one. Yes, the stop down device was always used.

 

It's crazy that these things were ever sold. Hard to think that someone, somewhere didn't suffer eye damage from them.



#199 DocFinance

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Posted 06 October 2014 - 07:25 AM

I'm surprised that new scopes still come with the aperture stop built into the end cap, just like 30 years ago.  I use the stops when looking at the moon.



#200 terraclarke

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Posted Yesterday, 09:30 AM

Often those that still do are shorter achros and so it allows a way of reducing the CA on brighter objects. My 6" F5 Omni XLT refractor is my favorite deep sky scope and it handles color pretty well with the Celestron XLT coatings in its innate state, but when I use the aperture stop on the lens cap, it goes from 152mm down to 114mm and becomes an  F6.67 and gives it more capability on bright targets.








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