Kellners! thoughts, mini review, and photo

Just opinions, no facts here. Jump to the bottom for performance review.

I recently acquired some antique kellners from the 80's. From reading S&T's from that era, it appears that eyepiece choices for the average amateur were the Huygenian, Ramsden, Kellner, Ortho, and Erfle. Of these 5 only the ortho appears to remain a popular choice. They sell fast here, that for sure. Guidebooks generally advise against Huygenian and Ramsden ep's, rate Kellners as the minimum acceptable,and praise the orthos and Erfles.

Today, where does one find these ep's? Huygenians and Ramsdens can be found at the auction site, usually as dinky ep's to go with dinky scopes there. I have never seen these ep's advertised in my time astronomical (1997 to present)

Kellners are still around. Meade MA's, Celestron SMA's, Edmund RKE's, and the 3-element, 2-inchers like the Celestron Elux are all Kellners according to various internet sources. Also the crosshair ep's in finderscopes.

Orthos and Erfles are still made by University Optics and Antares, but are rarely seen. Who's buying these?

The Kellners and Orthos of the pre-80's have been replaced by the plossl. The plossl explosion of the 80's may have been started by Televue in 1980. Compare a 1980 magazine with a 1984.

In the attached photo are several ep's. The top row are the Meade MA's, old Japan style and later Chinese type. The Japan is quice the nice ep and superior to later models. It has better coatings, larger eye lens, more eye relief, and better construction overall. Note the reflections.

Bottom row left is a generic silvertop 25pl and a 25 Celestron Kellner. The reason for the plossl's ascendance is quite clear: larger eye lens, wider fov, sharper in fast scopes, and (cheaper to manufacture?)

The bottom right are two identical Japan 40 Kellners, one is an Optica b/c and the other a Celestron. In the 1980 mag there were at least 5 different advertisers selling the same ep's.

How well do they work? Very well. In a 178mm f/15 the Celestron Kellners gave sharp, bright images with a narrow fov. The Japan Meade MA was right up there with the plossl, but with less fov. I also have an Edmund 28mm RKE. Its sharp in the middle, but the outer 1/3 is not.
In 80mm f/6 and 50mm f/4 the Kellers gave pleasing, sharp views with minor edge distortion. My 6mm ortho wont reach focus in these scopes, cant get close enough. The RKE is only sharp in the center, the outer 4/5 horribly distorted. Next week I plan to try these ep's in a 317mm f/5.

Its fun to experiment with these fossil ep's, they work very well. I have a curiosity about eyepieces that are no longer available. Makes me appreciate the Panoptics and Naglers all the more.

Regards
John R

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>>>Its fun to experiment with these fossil ep's, they work very well. I have a curiosity about eyepieces that are no longer available. Makes me appreciate the Panoptics and Naglers all the more.
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John: Older eyepieces are an interesting topic, glad you brought it up. I think Billy Rose does some serious comparisons of many of the older eyepieces.

I enjoy these eyepieces but I do not consider them necessarily "antiques" or "fossil" eyepieces. I consider them simpler designs that are, as you point out, still used.

I have a set of Meade Circle T orthos that are from the late 70's, early 80's along with a matching "Multi-coated" MA 40. These are Japanese made and provide quite amazing views, in the appropriate scope, sharp and free from internal reflections and "scatter." In my 6 inch F8 Newtonian (RV-6), I much prefer them to designs with more elements like Naglers etc. With the tracking mount, a 40 degree field of view is more than enough. A 20mm Celestron Erfle completes that set of eyepieces and provides surprisingly sharp widefield views in the appropriate scope.

In my thinking, these eyepieces are probably better termed "classic" or as I prefer to call them "simple eyepieces" and include them with the Plossls. These are eyepieces, MA's, Orthos and Erfles, that in a slower scope provide all the sharpness of a fancy design with probably better "scattered" light control but a narrower field of view, its a trade off but means these eyepieces are still competitive.

To me and antique or fossil eyepiece would be something along the lines the Criterion Achromatic Ramsdens, these give reasonable views but with a significantly narrower field of view than the Kellners and orthos but with no apparent advantages.


My thinking is these eyepieces are from a different era when scopes were slower, there was less light pollution and everyone had tracking mounts. In my F4 DOB, the issues are quite different, one is fighting for field of view and edge astigmatism. Exit pupil is not a limitation...

Jon

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"Orthos and Erfles are still made by University Optics and Antares, but are rarely seen. Who's buying these?"

I think a large percentage of amateurs have at least one and many have complete sets of the University Optics Orthoscopics. In my neck of the woods (Northern California) these Orthoscopics are about as common as the Televue Plossls, and are only slightly less common than the modified Plossls that in the past were bundled with many new telescopes (Meade Series 4000, Celestorn Ultima, etc.). Almost anyone you meet at a local star party has one or two for planetary and lunar observation, and for sharing at star parties. Although they have a narrower field of view than a similar focal length Plossl, they have better eye relief and are actually easier to use for extended periods of time at high magnification.

University Optics also still sells Japanese made Kellners in 12mm, 20mm and 40mm focal lengths for about $50 each. Unlike their Orthoscopics which are "multi-coated" and their HD Orthoscopics which are "fully multi-coated", the Kellners are merely "fully coated".

I've never used the University Optics Kellners, but I have owned Meade MA made in Japan eyepieces and Edmund RKEs, so I can't tell you how the University Optics models stack up to the others you mention.

- Jim

John, great write-up and sharing of your thoughts!

John,

I have a K 25 Kellner, just like the one on your picture and I love it. I bought it from Coulter (I think!) in the mid-70's.

I use it happily with my 4.5" f-4 and my 90mm f11.1. Stars bloom a bit near the edges with my f-4, but are pretty clear with the f-11 to the edge.

Rick