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Amazing Kellner 12.5mm eyepiece

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#1 larrytOMC200

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Posted 03 July 2020 - 04:02 AM

Hi all,

        Just thought I would share my experience when observing the moon on 2nd July, after a long spell of inclement weather, the skies cleared and Luna beckoned. The seeing was quite good at times, I managed some nice images and decided I would try out an old Kellner eyepiece that I have had for decades, (truthfully forgot about).

I had used some plossels and sky watch panorama eyepieces before curiosity got the better of me after finding the Kellner.

I was amazed at the crisp, colour free and detailed  image I was looking at. (I was using my OMC200 F20 Maksutov). I will definitly be using this eyepiece again!

Anyway, just thought I would give credit where credit is due, as regards, I suspect undervalued and neglected occulars. Keep well.   Larry


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#2 TOMDEY

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Posted 03 July 2020 - 04:18 AM

Yeah, Kellners perform magnificently at F/20.    Tom


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#3 PETER DREW

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Posted 03 July 2020 - 04:48 AM

No surprises there.



#4 j.gardavsky

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Posted 03 July 2020 - 05:38 AM

Still keeping my Carl Zeiss Jena f=20mm Kellner, and also having one old CZJ orthoscopic Kellner.

 

The old Kellners are still super on some difficult nebulae and even on the fast telescopes. The drawback is the short eye relief.

 

Thank you for reminding this old piece of glass,

JG


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#5 CharlieB

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Posted 03 July 2020 - 06:27 AM

This Nikon 10x (25mm) Kellner is a fine eyepiece.  Quite sharp all the way to the edge and it has decent eye relief. Light transmission is excellent.

 

Nikon 10x Kellner.jpg

 

 


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#6 BillP

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Posted 03 July 2020 - 07:18 AM

Yes, I try to only use scopes that have at least f/8 or longer focal ratios.  The reason is exactly as you saw with your scope, the simple eyepieces perform amazing!  With the complex wide fields you can almost "feel" all the glass between you and the object, even with the best premiums.  However, the old classic designs with just their 3, 4, or 5 elements behave like there is nothing between you and the target showing views with unparalleled crystal clarity.  Wide fields of course have their place, but when you want an experience that is like being there, there is nothing like a long focal ratio instrument and a classic eyepiece IMO.


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#7 Thomas_M44

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Posted 04 July 2020 - 05:42 PM

Hi all,

        Just thought I would share my experience when observing the moon on 2nd July, after a long spell of inclement weather, the skies cleared and Luna beckoned. The seeing was quite good at times, I managed some nice images and decided I would try out an old Kellner eyepiece that I have had for decades, (truthfully forgot about).

I had used some plossels and sky watch panorama eyepieces before curiosity got the better of me after finding the Kellner.

I was amazed at the crisp, colour free and detailed  image I was looking at. (I was using my OMC200 F20 Maksutov). I will definitly be using this eyepiece again!

Anyway, just thought I would give credit where credit is due, as regards, I suspect undervalued and neglected occulars. Keep well.   Larry

Larry,

 

Have you had the opportunity to also try any Edmund RKE eyepieces in your f/20  Mak?

 

The RKE is a minimalist  3-element design which works particularly well in scopes of f/10 and slower.

 

They'd should be right at home in your Mak.

 

Edmund Optics still sells the RKE in four FL's for $85 each


Edited by Thomas_M44, 05 July 2020 - 03:05 PM.

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#8 Peter Besenbruch

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Posted 05 July 2020 - 01:20 AM

...The seeing was quite good at times, I managed some nice images and decided I would try out an old Kellner eyepiece that I have had for decades, (truthfully forgot about).

I had used some plossels and sky watch panorama eyepieces before curiosity got the better of me after finding the Kellner.

I was amazed at the crisp, colour free and detailed  image I was looking at. (I was using my OMC200 F20 Maksutov).

A Coke bottle would look good at f20.

 

That said, a number of the older designs look pretty good in a long f-ratio instrument. Mine is "only" an f15, but I am having excellent results with the WA series of eyepieces. At f7.5 they struggle a bit, and the longer focal lengths fall down completely. At f15 they shine. They outperform the UFFs (better contrast), and the 12mm matched my Takahashi 12.5 so closely in contrast, that It retired the more expensive Tak.

 

When you go long, it's a whole other word when it comes to eyepiece selection, and I'm not surprised your Kellner did so well.


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#9 BillP

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Posted 05 July 2020 - 09:04 AM

When you go long, it's a whole other word when it comes to eyepiece selection, and I'm not surprised your Kellner did so well.

Shhhhh!  Don't let the secret out on how much fun (and inexpensive) the hobby can be by simply choosing focal ratios wisely!


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#10 steve t

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Posted 05 July 2020 - 11:46 AM

funnypost.gif 



#11 j.gardavsky

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Posted 05 July 2020 - 12:29 PM

Here are the classic Zeiss Kellners (f=20mm):

At left is the old orthoscopic corrected Kellner.

At right is the last version of Kellner for the professional use in microscopy.

 

Decades ago, I have been using that one at right on the fast refractors at low magnifications.

Excellent contrast, and high transmissivity also on the short blue wavelengths.

CZJ Kellners.jpg

 

Thank you for looking,

JG


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#12 Thomas_M44

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Posted 05 July 2020 - 03:01 PM

A Coke bottle would look good at f20.

 

That said, a number of the older designs look pretty good in a long f-ratio instrument. Mine is "only" an f15, but I am having excellent results with the WA series of eyepieces. At f7.5 they struggle a bit, and the longer focal lengths fall down completely. At f15 they shine. They outperform the UFFs (better contrast), and the 12mm matched my Takahashi 12.5 so closely in contrast, that It retired the more expensive Tak.

 

When you go long, it's a whole other word when it comes to eyepiece selection, and I'm not surprised your Kellner did so well.

I'm really leaning towards eventually getting a second refractor of f/15 for lunar/planetary and other high magnification viewing, likely a 4" or possibly a 5".  A classic Fraunhofer doublet of excellent quality in a sturdy adjustable lens cell is what I'm thinking.

 

I'd absolutely keep my TV85 for it's portability/versatility and lush wide-field capabilities in particular.

 

The ability to achieve crisp high-magnification views with simple 3-4 element EP's of moderate FL and decent ER holds a  strong appeal for me. My favored prism diagonals would also work better at a slower F-ratio.

 

A two-lens doublet objective and, for example, a 3-lens RKE EP --that's very little glass between the eye and the observed object.


Edited by Thomas_M44, 05 July 2020 - 03:07 PM.

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#13 j.gardavsky

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Posted 05 July 2020 - 03:30 PM

Larry,

 

Have you had the opportunity to also try any Edmund RKE eyepieces in your f/20  Mak?

 

The RKE is a minimalist  3-element design which works particularly well in scopes of f/10 and slower.

 

They'd should be right at home in your Mak.

 

Edmund Optics still sells the RKE in four FL's for $85 each

An alternative to the RKE are the (field stop 2 - 1) Leica HC Plan 10x/20 M (f=25mm) product #507802,

or the Carl Zeiss E-Pl 10x/20 (f=25mm) (field stop 2 - 1), product # 44 42 31 or #44 42 32.

 

See also https://www.cloudyni...my-microscopes/

 

Best,

JG



#14 Magnetic Field

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Posted 05 July 2020 - 05:21 PM

Still keeping my Carl Zeiss Jena f=20mm Kellner, and also having one old CZJ orthoscopic Kellner.

 

The old Kellners are still super on some difficult nebulae and even on the fast telescopes. The drawback is the short eye relief.

 

Thank you for reminding this old piece of glass,

JG

Out of interest.

 

What is the point of using a Kellner these days?

 

I mean every Ploessl (also the mediocre ones) outperforms a Kellner.

 

Isn't this a waste of time using a Kellner? You don't get back the time that you have used behind the eyepiece with your Kellner.


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#15 shaesavage

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Posted 05 July 2020 - 07:11 PM

Out of interest.

 

What is the point of using a Kellner these days?

 

I mean every Ploessl (also the mediocre ones) outperforms a Kellner.

 

Isn't this a waste of time using a Kellner? You don't get back the time that you have used behind the eyepiece with your Kellner.

I strongly believe in experimentation because everyone has different tastes. I have Pentax SMC orthos, Nikon orthos, and TMB Monocentrics for critical observing. A couple weeks ago while observing the moon with my Tak 76dcu, I decided to only use some Huygens that I have (25mm Goto, 25mm Zeiss Jena, and a 16mm Zeiss Jena). I forgot how good the Huygens are. My high end glass is better, but it's hard to argue against the cost/performance ratio for these old designs when done right! 


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#16 SandyHouTex

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Posted 05 July 2020 - 08:01 PM

Out of interest.

 

What is the point of using a Kellner these days?

 

I mean every Ploessl (also the mediocre ones) outperforms a Kellner.

 

Isn't this a waste of time using a Kellner? You don't get back the time that you have used behind the eyepiece with your Kellner.

Actually if you go here:

 

https://telescope-op...berration_2.htm

 

You’ll see at f/10, and longer, the Achromatic Pair (which is what present day Plossls are) are no better than Kellners.


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#17 MartinPond

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Posted 05 July 2020 - 08:08 PM

Out of interest.

 

What is the point of using a Kellner these days?

 

I mean every Ploessl (also the mediocre ones) outperforms a Kellner.

 

Isn't this a waste of time using a Kellner? You don't get back the time that you have used behind the eyepiece with your Kellner.

On a long barrel, a Kellner can produce better contrast than a Plossl,

   especially if the Plossl is of the 53-degree afov dimple-faced type.

Near as I can tell with my contrast test target, anyway.....at F10

Many of those classic Kellners have internal threading and blacking

  that only goes into the finest Plossls now.

 

Unless you have tried a good assortment of representatives

  on a proper target, you might be making a very hasty generalization.

  Beware the side-effects of tribal pride.


Edited by MartinPond, 05 July 2020 - 08:10 PM.

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#18 saemark30

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Posted 06 July 2020 - 01:02 AM

The problem with Kellners is seeing the dust in the field lens. They are not fully corrected for color. At long FR the dust effects are very bad. In the old days the Ortho was the most expensive design and Kellners were half of that. Today the ORs are  reasonably priced, have no visible distortion and better coatings.

Notable exception is the Zeiss aspherical 3 element eyepiece but that is not a standard Kellner! 

The RKE is an improvement but better coatings would be desirable.


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#19 j.gardavsky

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Posted 06 July 2020 - 03:15 AM

The Zeiss aspheric 3-element EP is an aspherized (filed stop - 2 - 1) König, it has nothing to do with the Rand's RKE. The RKE is regarded as a side line in the optics developments, available still from Edmund Optics.

I have a set of the Zeiss E-Pl in my drawer, documenting the iterative development of the design.

 

The Kellner A-series from Carl Zeiss Jena is a keeper, like the Zeiss Abbe orthos. You simply have it, even if you don't use it frequently.

 

Best,

JG


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#20 csrlice12

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Posted 06 July 2020 - 10:09 AM

I donno....I have a Pentax 12.5mm Kellner, and in my f10 refractor on the moon, it has a clarity that isn't matched by most of my premium eyepieces...


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#21 saemark30

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Posted 06 July 2020 - 10:28 AM

The Zeiss are definitely not RKE, when I wrote RKE I meant the Edmund eypieces, that is why I say they need better coatings i.e. multicoatings. 

The Pentax Ks are killer and very transparent. Problem is they still have some color residue where the OR is perfect.

One has to be careful not to get dust on the field lens or that would be very visible. The ones that came with their refractors also were single coated.

 

I like to hear the history of the Zeiss 3 element aspheric as this is what a state of the art 3 element eyepiece should be like!


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#22 j.gardavsky

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Posted 06 July 2020 - 11:53 AM

The Zeiss are definitely not RKE, when I wrote RKE I meant the Edmund eypieces, that is why I say they need better coatings i.e. multicoatings. 

The Pentax Ks are killer and very transparent. Problem is they still have some color residue where the OR is perfect.

One has to be careful not to get dust on the field lens or that would be very visible. The ones that came with their refractors also were single coated.

 

I like to hear the history of the Zeiss 3 element aspheric as this is what a state of the art 3 element eyepiece should be like!

In fact,

there is not much known about the historical development of the Zeiss E-Pl (extra planar) eyepieces.

I can contact some people on the German Mikro-Forum, where I am also a member, maybe somebody knows more.

My conclusions have been so far drawn from a few E-Pl, I have in my collection.

 

Best,

JG



#23 JamesDuffey

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Posted 06 July 2020 - 12:13 PM

Actually if you go here:

 

https://telescope-op...berration_2.htm

 

You’ll see at f/10, and longer, the Achromatic Pair (which is what present day Plossls are) are no better than Kellners.

From that link the achromatic pair look better off axis at 7 and 10 degrees than the Kellner, unless I am missing something. 



#24 Magnetic Field

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Posted 06 July 2020 - 12:57 PM

From that link the achromatic pair look better off axis at 7 and 10 degrees than the Kellner, unless I am missing something. 

To put lipstick on a Kellner. Not convinced.

 

Reminds me on the Questar. You can have the most perfect and expensive 90mm Maksutov in the world. But my cheap Vixen VMC 110L will blow it out of the water for double stars for example.

 

I will pass the most expensive Kellner in the world for a cheap Vixen NPL.



#25 MartinPond

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Posted 06 July 2020 - 01:45 PM

I donno....I have a Pentax 12.5mm Kellner, and in my f10 refractor on the moon, it has a clarity that isn't matched by most of my premium eyepieces...

I have a Zeiss 20mm Kellner from 6x30 Silvarems  (~1915)

  that is astoundingly clear and true-colored.

 

  And....it is even "uncoated".

  I put that in quotes because some glasses actually grow a coating.

  That's how coating was originally discovered.  Sometimes, later,  lenses

   were baked and/or chemically basted to grow that transitional layer

   . They called that "luminized" sometimes.

    Still, pretty impressive for contrast, from a 1915 EP.

 

   The lining is the Zeiss standard fine threads with lampblack.

 

  To  address what was said about the field lens being nearly in focus;

    that is true of the Kellner, the 1,2 Konig, and the Ramsden, if

    a longer-fl Ramsden is spread to improve abberations

    beyond the standard formula Ramsden.

    (you can afford to do that when the eye relief is large to start)

   

But back to the (~1915) Zeiss 20mm Kellner and field lens smutz:

    I did need to clean the glass, especially the field lens,

    to maximize the contrast.

 

---------------

 

The RKE is a 1.2 Konig that has been stretched in spacing,

  for less field with greater geometric accuracy.  Strangely,

  a stretched-1,2 Konig was used for many decades, maybe

  since ~1930s, as an eyepiece to directly read instruments like

  radiation dosimeters, pressure gauges, precision compasses,

    monitoring meters, and sextants. 

   The RKE Seems like a parallel develop, made later on,

   in ignorance of instrument Konig.  The RKE also uses

   some low-ED glass, of course.

   The RKE drawing at Edmund is a bit coy....

       the spacing is well off from the patent.

   Since Edmund publishes extensive distortion data (to boast),

    I wonder if it might be the most 'orthogonal' eyepiece.

 

As far as other properties of the RKE, I don't know about contrast

   compared to an Abbe, for example.  

A Plossl's advantage might be a bit less chromatics at the field edge,

  which is not noticeable in daylight or for most planetary, but can be

  noticed for those teeny-dot stars. 


Edited by MartinPond, 06 July 2020 - 01:49 PM.

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