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Use of vintage eyepiece sun filters.

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#201 Jim Curry

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Posted 28 October 2014 - 07:44 PM

Well, after having a drawer full of these solar eyepieces knocking around for decades I put one to work last week as a monocle filter for sunspot viewing and eclipse catching.

 

Jim


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#202 joecomet

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Posted 28 January 2015 - 08:08 PM

When I found the family old five section 70mm refractor of 1800's vintagea at age 12, it had a smoked lens that fliped over the first lens of the eyepiece.  With nobody in the family that new anything about using the scope , I was on my own.  Dumbutt me pointed (had it on a camera tripood) it at the sun an rotated the first section to focus.  I don't know how I managed not to burn my retna, as this sun lens then fliped over and exposed me to what ever mag that old lens was giving.  Ach will! Nobody said growing up was safe or easy.  Lucky to still be here at 75.

Joseph

20" dob/sold

15" dob/sold

Back to the old Tom Clark built (Coulter mirror) 10"


Edited by joecomet, 28 January 2015 - 08:14 PM.


#203 Joe Cepleur

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Posted 08 February 2015 - 11:19 AM

In a manual supplied with a Jason refractor, there is evidence that, by 1967, Jason was hedging its bets against breakage of eyepiece solar filters. Hesitancy against using them is found in that year's edition of "Jason*Empire Telescope Techniques with Illustrated Studies," published by Jake Levin & Son, Inc., a manual included with Jason telescopes. On Page 20, "Advanced Celestial Study -- Daytime Viewing #14" reads, with the boldface and capitals as they appear in the original:

 

"Though many telescopes come equipped with a red sun filter, NEVER rely entirely on this for eye protection. Never view the sun without doing these two things: (1) Have the sun filter in position, and (2) wear dark glasses or use dark developed film... It is better to reduce the amount of light from the sun by using the smaller diameter opening on the objective lens. Most telescopes have a smaller inner cap as part of the moisture cap."  

 

Those are all the right steps to take to reduce the risk, yet even Jason knew at the time that it was better not to use these filters at all. The prior study dismisses them as unneeded. "Advanced Celestial Study -- Daytime Celestial Viewing #13" first describes how to use or even make your own solar projection screen, and then states:

 

"This is an added safety protection and you can see as much from viewing the sun in this method as viewing it directly." 

 

It appears that there was inertia in the marketplace, as though people expected to receive eyepiece solar filters with their new telescopes for some time after at least this manufacturer was nervous about delivering them. 

 

Special thanks to member jungus57, who sent me this book, hoping it would find an appreciative home. How suitable that it should help unravel the history of unsafe eyepiece solar filters.



#204 Mr Magoo

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Posted 08 February 2015 - 11:50 AM

Has anyone ever heard of a 4 draw telescope with a sun filter? One of my club members was given an old 4 draw scope with no other marking except France on the cap and it has a filter that flips into place with the turn of a knob. He is assuming it is a solar filter. I told him to please not try it on the sun. 



#205 Joe Cepleur

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Posted 08 February 2015 - 12:27 PM

...a 4 draw telescope with a sun filter ... flips into place with the turn of a knob.


Possibly an old naval telescope with a filter for spotting ships that would otherwise be lost in glare?

#206 combatdad

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Posted 09 February 2015 - 06:04 PM

Unitron's official position on the use of their Sun Glass filters: Technical Bulletin, Sun Glass Filter, April 1, 1979

 

Dave

 

http://www.unitronhi.../inventory02-2/



#207 Rich (RLTYS)

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Posted 10 February 2015 - 05:55 AM

Unitron did the right thing.  :waytogo:

 

Rich (RLTYS)



#208 Bob Myler

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Posted 10 February 2015 - 07:19 AM

Mine are 'very dear' ($$$) to me - maybe there's a buyback program?.... :cool:



#209 Chuck Hards

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Posted 10 February 2015 - 09:01 AM

You know these old sun filters work great for naked-eye views of the sun, no safety problems at all if not used with a telescope.  I was thinking of making solar spectacles with a pair of them.  Kind of a steam-punk, comic-book look.  Be nice for the eclipse in 2017.


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#210 Joe Cepleur

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Posted 10 February 2015 - 09:12 AM

So, by 1967, Jason was hedging against eyepiece sun filters, and by 1979, Unitron eliminated them as a standard accessory. What happened in between; when did other manufacturers stop supplying these? Was their elimination voluntary, and due to a growing sense of safety and best practice, or was there a law suit? 

 

Somewhere, maybe even earlier in this thread or in a link from it, I read about a 19th-Century eyepiece filter of a different design. It was a thick plug of glass, not a thin plate, and it was fused to its brass housing in such a way that breakage was unlikely. Trouble was, it also lacked any protection against ultra violet light, so those who used them lost sight slowly. I can imagine, but not confirm, a history: The glass rolling machine is invented, so plates of smoked glass become cheap; then, plastics come along, so disks from thin plates become easy to mold into threaded cells. Seems to work well enough, especially with the aperture stop no one would actually use; so, next thing you know, astronomers everywhere are at risk for broken shards of glass in their eyes. 



#211 greju

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Posted 10 February 2015 - 01:13 PM

You know these old sun filters work great for naked-eye views of the sun, no safety problems at all if not used with a telescope.  I was thinking of making solar spectacles with a pair of them.  Kind of a steam-punk, comic-book look.  Be nice for the eclipse in 2017.

Do you have something to back this up or is it just your opinion? You can go ahead and chance it if you want but I will stick with a modern solar filter. :confused:



#212 Jim Curry

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Posted 10 February 2015 - 10:16 PM

 

You know these old sun filters work great for naked-eye views of the sun, no safety problems at all if not used with a telescope.  I was thinking of making solar spectacles with a pair of them.  Kind of a steam-punk, comic-book look.  Be nice for the eclipse in 2017.

Do you have something to back this up or is it just your opinion? You can go ahead and chance it if you want but I will stick with a modern solar filter. :confused:

 

For quick glances at the sun, what's the issue?  I watched that big set of sunspots this past fall with my Unitron filter I have with me.

The problem with them is/was the heat from the focused light of the scope cracked them.

Jim



#213 mikey cee

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Posted 10 February 2015 - 10:38 PM

 

 

You know these old sun filters work great for naked-eye views of the sun, no safety problems at all if not used with a telescope.  I was thinking of making solar spectacles with a pair of them.  Kind of a steam-punk, comic-book look.  Be nice for the eclipse in 2017.

Do you have something to back this up or is it just your opinion? You can go ahead and chance it if you want but I will stick with a modern solar filter. :confused:

 

For quick glances at the sun, what's the issue?  I watched that big set of sunspots this past fall with my Unitron filter I have with me.

The problem with them is/was the heat from the focused light of the scope cracked them.

Jim

 

Ditto!



#214 astronomy-shoppe.com

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Posted 11 February 2015 - 12:00 PM

I have had a sun filter crack on me quite a while ago. However,my Unitron 128 came with a Herchel wedge and the filter worked fine and safe with that.

 

Tony C

 

 


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#215 Jim Curry

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Posted 11 February 2015 - 09:08 PM

Hi Tony:

 

No one is proposing utilizing these for telescopic use, it's well established they're not safe.  The last few posts were referencing using them in straight thru monocle mode.  I agree, white light viewing I prefer a Herschel wedge.

 

Jim



#216 mikey cee

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Posted 11 February 2015 - 10:23 PM

How does one use these old screw in sun filters with a Hershel wedge? Seems to me the Sun's image would be too dim afterwards.  :confused:



#217 greju

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Posted 12 February 2015 - 12:18 AM

"Only use filters from reputable sources, and never use a "solar filter" that screws into an eyepiece. As Richard Hill states in Observe and Understand the Sun:
"Observing the sun is the only inherently dangerous observing an amateur astronomer can do. Be aware of this at all times and take all necessary precautions. If you do not know a filter or procedure is safe then do not use it! Always err on the side of safety. An eye once damaged is forever damaged. Filters that let too much INFRARED light through can burn an eye if used visually. There is NO PAIN when this happens. Burned retinas can not be repaired. Excessive ULTRAVIOLET light has been shown to cause cataracts. So be very careful."

 

Unless someone can convince me that these old sun filters are anything other than green glass with absolutely no filtering capabilities for both infrared and ultraviolet light I will say, yet again, do not use these filters in any way shape or form if you care for your eyes at all. 



#218 astronomy-shoppe.com

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Posted 12 February 2015 - 11:28 AM

The Herssel wedge that came with my unitron was .96    I placed the filter after the wedge in one the eyepieces, Unitron also supplied a dark filter that went on top of the eyepiece but I can't post a photo here.  Worked fine with the wedge.



#219 Chuck Hards

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Posted 12 February 2015 - 07:32 PM

I am looking for a physicist at the local university who can help me get precise transmission characteristics for these old filters.

 

I'm kind of astounded that anybody wouldn't see the difference between using them for naked-eye viewing, and placing them on an eyepiece and actually using them in a telescope.  It is common knowledge that they are basically welder's glass- completely safe in #13 & #14.  These filters are still produced today, they are not antique "colored glass" from before the Industrial Revolution.  The warning is to never use them in a telescope, on an eyepiece, where the concentrated solar energy can overheat and crack them.  Of course they should never be used in such a configuration. 

 

I had one crack on me, when I was young, back in the 60s.  I've never used one with a telescope since.  But just holding it up to your eyeball does not subject it to the heat stress that a telescope does.

 

I'll report my findings in this thread or it's replacement, when I have something to share.  I will report no matter what I find out.


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