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Use of vintage eyepiece sun filters.

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#226 Joe Cepleur

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Posted 07 April 2016 - 10:22 AM

Sun filters were expected to be used with Huygenian eyepieces where the focal plane is actually inside the eyepiece and so the filter is far from it and probably not subject to great heat concentration.

 

In theory, perhaps, and an interesting point; yet, in the history of broken Sun filters, surely many broke while used with the Huygens sold with many classic telescopes. Using an eyepiece filter with a Huygens eyepiece places the filter within an inch or two of the most concentrated rays, exposing it to far more heat than, for example, a perfectly safe filter over the objective. One hopes readers would not misinterpret this as meaning it were okay to try using an aging eyepiece Sun filter with a Huygens eyepiece. Don't do it. Not worth the risk! 


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#227 Mr Magoo

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Posted 04 May 2016 - 06:02 PM

Not for the squeamish maybe, but the proof is in the seeing so to speak. http://www.scienceal...ugh-a-telescope


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#228 Rich (RLTYS)

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Posted 05 May 2016 - 05:36 AM

Most interesting but absolutely true.

 

Rich (RLTYS)



#229 saemark30

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Posted 29 July 2016 - 09:53 AM

Does anyone have a sun filter of 1.25" size they can donate for a experiment?



#230 twhite

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Posted 07 October 2016 - 03:57 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:

As an experiment, I tried this while at OTSP this year with a classic Herschel Wedge in the same 60mm f/7 scope I have set up side-by-side with my 60mm Coronado.  It uses the same 36.4mm threaded visual backs that Vixen does, and I happen to have a 24mm visual back, so -- let's see what happens!

 

Yes, this image is *far* too dim afterwards.  I had hoped it would not be so that I could use my classic scopes for solar as well, but sadly, that won't be the case.

 

The filters that I have a very, very dark indeed -- too dark, in fact.  I know I've seen lighter filters -- and some that have a more greenish tint to them -- so I may have to try one of those next, should I lay hands on one again.  I do have one of the Unitron-branded wedges and filters, but I'm not a fan of that setup.

 

So I guess I'll stick to using my 1.25" Lunt, even though I have to use an additional ND filter with it.  Better safe than sorry!



#231 Ken Watts

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Posted 11 January 2017 - 09:56 AM

I have a lightning bolt shaped scar on my retina from the mid 1970's when my filter cracked.  Was on a 6" f/8 newt on about the 20th time looking at sunspots.  DON'T play roulette with your vision!  Technology has come too far to use the old eyepiece filters.


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#232 photoracer18

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Posted 17 January 2017 - 04:03 PM

A Newtonian solar scope would have the secondary mirror replaced with a solar wedge mounted so the carrier has a central hole to dissipate the heat. Only ones I know this works with is a single arm secondary mount. You just have an extra one with the Herschel prism on it. I think Edmunds made them up for some of their reflecting telescopes back in the 50-60's time frame.


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#233 photoracer18

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Posted 19 January 2017 - 03:18 PM

Another thing a Herschel wedge is good for is as a light reducer for viewing the Moon at full. Wonderful reducer of glare and brightness, and it really helps the contrast. Because its a precision optical surface I think they are much better for detail than the average Moon filter. I used an old Optica b/c one I acquired in the 60's in both a Unitron 2.4" I had and a Pentax 85 I acquired close to 2 decades later. Still have it but the prism edge got broken off due to a fall. I won't use it on the Sun but it still works fine on the Moon.


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#234 oldscope

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Posted 03 April 2017 - 08:03 AM

Yesterday, the sun had some great active groups, so I took out my 3.5 inch Brashear, stuck on a Brashear Herschel wedge and did some great observing. The wedge was designed with a three-filter wheel just below the eyepiece holder. The "neutral" density filters are actually tinted a little ... a bit blue green, but quite comfortable to use. The darkest is too dark for that small a refractor, but the other two filters give a choice of brightness.

 

The unit's heat 'exhaust is simply a hole directly in line with the optical path and if there is a hitch with this unit, it's that you need to be careful that your crotch or clothes are not in line, too! I just melted the material in a nice down vest because I was not paying enough attention and it's the third or fourth time I've done this over three decades of using it. bangbang.gif  It's like an old cartoon. I smelled something burning and ... it was me! Apparently Tom and Jerry have nothing on me.

 

I'll be bringing the wedge and scope to NEAF and if the sun's out, stop by and try your hand at torching your own clothes! The sacrifices we make for this hobby. Yeesh.

 

Bart F.

 

 


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#235 CharlieB

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Posted 03 April 2017 - 11:23 AM

I've done the same thing with my .965 Herschel wedge more than once.  Now I just view "side-saddle" and always remember to cap off the finder.  I'll be bringing mine to NEAF to do some small scope white light through some 40 & 50mm scopes. 

 

With my Optica b/c ND filters, I get a slightly red-tinted view.

 

I'll be looking for you, but the Sun may not cooperate.

 

Charlie



#236 deSitter

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Posted 03 April 2017 - 11:55 AM

Yesterday, the sun had some great active groups, so I took out my 3.5 inch Brashear, stuck on a Brashear Herschel wedge and did some great observing. The wedge was designed with a three-filter wheel just below the eyepiece holder. The "neutral" density filters are actually tinted a little ... a bit blue green, but quite comfortable to use. The darkest is too dark for that small a refractor, but the other two filters give a choice of brightness.

 

The unit's heat 'exhaust is simply a hole directly in line with the optical path and if there is a hitch with this unit, it's that you need to be careful that your crotch or clothes are not in line, too! I just melted the material in a nice down vest because I was not paying enough attention and it's the third or fourth time I've done this over three decades of using it. bangbang.gif  It's like an old cartoon. I smelled something burning and ... it was me! Apparently Tom and Jerry have nothing on me.

 

I'll be bringing the wedge and scope to NEAF and if the sun's out, stop by and try your hand at torching your own clothes! The sacrifices we make for this hobby. Yeesh.

 

Bart F.

You've taken 1st place over the guy who left his truss Dob on the back porch after a night out - the Sun came up, bounced off the exposed mirror, and nearly burned his house down :)

 

-drl


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#237 Joe Cepleur

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Posted 03 April 2017 - 03:52 PM

The unit's heat 'exhaust is simply a hole directly in line with the optical path and if there is a hitch with this unit, it's that you need to be careful that your crotch or clothes are not in line, too! I just melted the material in a nice down vest…

This certainly illustrates the amount of heat that is better directed to melting one's vest than shattering an antique eyepiece filter in one's eye. 

 

Perhaps a little ATM spirit could improve that Herschel wedge? Could some metal plates be installed to dissipate the heat? Several layers of perforated steel might do the trick. They would become hot to the touch themselves, yet would also block the beam from attacking the astronomer. 



#238 terraclarke

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Posted 03 April 2017 - 04:01 PM

They can, and they have. They are generally unfinished metal and hinged, and are termed 'necktie savers'. They have been around for a long time. I have four wedges, classic and modern, and none were constructed without some provision for deflecting or dissipating the other 95 percent. 



#239 oldscope

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Posted 04 April 2017 - 05:07 PM

 

Yesterday, the sun had some great active groups, so I took out my 3.5 inch Brashear, stuck on a Brashear Herschel wedge and did some great observing. The wedge was designed with a three-filter wheel just below the eyepiece holder. The "neutral" density filters are actually tinted a little ... a bit blue green, but quite comfortable to use. The darkest is too dark for that small a refractor, but the other two filters give a choice of brightness.

 

The unit's heat 'exhaust is simply a hole directly in line with the optical path and if there is a hitch with this unit, it's that you need to be careful that your crotch or clothes are not in line, too! I just melted the material in a nice down vest because I was not paying enough attention and it's the third or fourth time I've done this over three decades of using it. bangbang.gif  It's like an old cartoon. I smelled something burning and ... it was me! Apparently Tom and Jerry have nothing on me.

 

I'll be bringing the wedge and scope to NEAF and if the sun's out, stop by and try your hand at torching your own clothes! The sacrifices we make for this hobby. Yeesh.

 

Bart F.

You've taken 1st place over the guy who left his truss Dob on the back porch after a night out - the Sun came up, bounced off the exposed mirror, and nearly burned his house down smile.gif

 

-drl

 

There are numerous anecdotes related to the sun, optics and flames ... the best one, quite true, happened at an observatory in California. An astronomer left a mirror in his car and the focused beam ended up torching the car.


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#240 joecomet

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Posted 04 April 2017 - 07:43 PM

How to nearly loose the site in one eye.  Take and old 5 section 1800's 60mm refactor, use a 'C' clamp to fasten it to and old wood photo tripod.  Flip over that dark glass filter in the eyepiece and focus on the Sun.  Then twist the last section to focus, and see the filter flip back to uncover the Sun's image at maybe 30X.  I was the 12 yr old dummy that reacted fast enough to keep from burning his eye. 

Got smart and saved up my "paper route" money and bought a Dynascope reflector 1952.

Have owned a Clark (Tom) 10" Dob, a Clark 15" Dob, and built an F6 20" Dob.  Now at 77 back down to my old 10".  Of course I peek though the TAS 14"Cas at our observatory when I get a chance.

Joseph 'comet' Haley  TAS Florida

 

 


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#241 joecomet

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Posted 04 April 2017 - 07:54 PM

Or how about Tippy D. the Miami Club Pres. who left his new Dob on the Winter Star Party field in a horizontal position.  A cat crawled  in tilted it to the Sun.  Scope and cat both survived, but burnt.


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#242 terraclarke

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Posted 04 April 2017 - 08:36 PM

Or how about Tippy D. the Miami Club Pres. who left his new Dob on the Winter Star Party field in a horizontal position.  A cat crawled  in tilted it to the Sun.  Scope and cat both survived, but burnt.

 

I imagine folks were alerted by the stink of burning cat hair! Poor thing. :(


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#243 ftwskies

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Posted 06 April 2017 - 04:11 PM

Has anyone ever tested the spectral properties of these old filters?  Are they just broad-spectrum green glass, or are they narrowband?



#244 terraclarke

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Posted 06 April 2017 - 05:20 PM

Most are made out of the same stuff as #14 welder's glass. This is a broadband, not a narrow band filter tho minimum transmission in the visibl wavelengths is at 600 nM (orange) and max is in the blue green around 440NM, resulting in a combined visual impression that is greenish-y llow.

 

Here is and a graph and table of transmission properties:

 

https://i.stack.imgur.com/u8yzV.jpg

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Edited by terraclarke, 06 April 2017 - 05:28 PM.

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