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32mm Kellner 1.25"?

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#1 bbqediguana

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Posted 19 September 2019 - 09:11 PM

Apologies if this is a dumb question. I did some Google diligence and I searched the forums, but I've come up short.

 

Was there ever a 32mm Kellner in the 1.25 inch format? Obviously the 32mm Plössl is pretty ubiquitous, and I have seen 32mm Orthos, but never a Kellner in that size. 25mm is the biggest I've seen.

 

If there aren't any - why would that be? Does the Kellner design perhaps not scale above 25mm?

 

Just curious. This all started with some Googling of the Starbase Orthos, and it wound up with a massive Numbers spreadsheet (that's the Apple version of Excel) and questions have arisen. smile.gif

 

Many thanks!

 

Rick



#2 Richard O'Neill

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Posted 19 September 2019 - 09:31 PM

I have a Celestron 30mm Kellner in 0.965" so I think 32mm in 1.25" should be easily doable, though I don't understand why anyone would want one - unless they enjoyed tunnel vision. flowerred.gif


Edited by Richard O'Neill, 19 September 2019 - 09:46 PM.

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#3 cookjaiii

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Posted 19 September 2019 - 09:36 PM

I have a 28mm Kellner in 1.25" that is unmarked but came with a Parks refractor.


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#4 bbqediguana

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Posted 19 September 2019 - 09:37 PM

I have a Celestron 30mm Kellner in 0.965" so I think 32mm in 1.25" should be easily doable, though I don't understand why anyone would want one. flowerred.gif

Cool! Thank you for that info - I have been Googling Celestron (Vixen) 30mm Kellner. So it doesn't appear to be a technical thing - likely just a market thing (as you state - who would want one?).

 

I'm just interested because I have a thing for simplistic eyepieces like Plössls, Orthos, Kellners, Königs, Erfles, etc. I even like Ramsdens and Huygens! jump.gif



#5 bbqediguana

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Posted 19 September 2019 - 09:39 PM

I have a 28mm Kellner in 1.25" that is unmarked but came with a Parks refractor.

That is cool! I maybe didn't widen my search enough - just looking for 32mm Kellner came up with some 2.00" models, but nothing for 1.25".

 

Thanks!



#6 TOMDEY

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Posted 19 September 2019 - 09:40 PM

Good question! I don't know the answer. Maybe the tube is too skinny to support its nominal field? ... But that would seem to also apply to the other eyepieces you mention. Note that there used to be a 28mm Edmund RKE eyepiece.    Tom

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#7 decep

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Posted 19 September 2019 - 09:57 PM

I believe I have seen ads for 40mm 1.25 kellners.
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#8 nicknacknock

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Posted 20 September 2019 - 12:28 AM

Seen 25mm and 40mm (Celestron) 1.25" Kellners, but not 32mm.


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#9 Jon Isaacs

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Posted 20 September 2019 - 05:53 AM

Hi:

 

I have not seen a 32mm Kellner.  I have, at least in theory, a 40mm Meade EWF MA.  It has the same color scheme as the Meade Series 2 Orthos and I consider it that's it of the same vintage.

 

4382656-Meade Or's 2small .jpg
 
I suspect the reason that one doesn't see 32mm Kellners goes like this:
 
The 32mm Plossl is very common because it maximizes the true field of view, maximizes the field stop for a Plossl in the 1.25 inch format.  This is not true of a Kellner whose AFoV is usually close to 40 degrees. The 40 degree EWF (it stands for Extra Wide Field) is pretty much that eyepiece. The AFoV is not wide but it gives that same floating in space feeling that eyepieces with large eye lenses with minimal surrounding body provide. 
 
Jon

 


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#10 bbqediguana

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Posted 20 September 2019 - 06:27 AM

 

Hi:

 

I have not seen a 32mm Kellner.  I have, at least in theory, a 40mm Meade EWF MA.  It has the same color scheme as the Meade Series 2 Orthos and I consider it that's it of the same vintage.

 

 
 
I suspect the reason that one doesn't see 32mm Kellners goes like this:
 
The 32mm Plossl is very common because it maximizes the true field of view, maximizes the field stop for a Plossl in the 1.25 inch format.  This is not true of a Kellner whose AFoV is usually close to 40 degrees. The 40 degree EWF (it stands for Extra Wide Field) is pretty much that eyepiece. The AFoV is not wide but it gives that same floating in space feeling that eyepieces with large eye lenses with minimal surrounding body provide. 
 
Jon

 

Ah yes! I forgot about the Meade MA's which are very similar to Kellners. I also have a 40mm 1.25" version of that eyepiece. I think you're right on about it maximizing the AFoV in the 1.25" format.

 

Thanks!


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#11 Jon Isaacs

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Posted 20 September 2019 - 06:32 AM

Ah yes! I forgot about the Meade MA's which are very similar to Kellners. I also have a 40mm 1.25" version of that eyepiece. I think you're right on about it maximizing the AFoV in the 1.25" format.

 

Thanks!

 

I imagine when Jaimo! sees this thread he will post pictures of at least five 32mm Kellners...  :)

 

Jon


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#12 CeleNoptic

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Posted 20 September 2019 - 12:18 PM

Does the Kellner design perhaps not scale above 25mm?

 

 

I have a 1.25" 40mm Japanese Kellner.

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  • 40mmKellner.jpg

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#13 Chuck Hards

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Posted 20 September 2019 - 12:25 PM

I have a full set of volcano-top Kellners, up to 40mm.  Though be careful, some of those 40mm labeled as "Kellners" are actually achromatic Huygens.  The focal plane lies between the eye and field lenses, easy to check.  

 

Edit:  Forgot that I have the very old UO 60mm Kellner in 2" barrel.  That's probably the longest FL Kellner I've ever owned.


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#14 Chuck Hards

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Posted 20 September 2019 - 02:49 PM

Here is the 60mm Kellner in comparison to a 2" 32mm Erfle of the same vintage.  There are no "scale effects" that preclude FL's longer than 25mm for Kellners.  You just get progressively narrower AVOF.

 

UO 2 inch 002.jpg


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#15 Chuck Hards

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Posted 20 September 2019 - 03:08 PM

Not 32mm, but pretty close.  A volcano-top 30mm K in 1.25", branded for Lumicon.  Circle-T so probably Tani.  Actually a really nice eyepiece on the longer FL refractors I use.  Probably at least 40 years old.

 

30mm K 001.jpg

 

 

 

 

 


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#16 bbqediguana

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Posted 20 September 2019 - 04:15 PM

Beautiful! Thank you so much. As always, I’ve learned some new things from this post.

Cheers!

Rick


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