Erfle's and Kellners

[koputai]

Has anyone around here owned/used the Kokusai Kkohki Erfle or Kellner eyepieces?

I expect the build quality is excellent, what do you think of them optically?

Cheers,
Jason.

[dannat]

i have looked thru an erfle..nice views - i wouldn't use them in a short scope (or barlow if i did) - but fro f8-f10 they give fairly wide views which are pleasing

[koputai]

Yeah, I have a couple of Erfle's already, and they're very nice, very easy on the eye. Less work than Naglers, more like a Panoptic. Don't get me wrong, I love Naglers, but the Pans and Erfles are just more comfortable, they feel more natural to the eye than wider or indeed narrower ep's.

I was just wondering what the performance of the Japanese made Erfle's and Kellners was like, if their throughput is better than the more modern eyepieces with more elements.

Cheers,
Jason.

[Wavytone]

Kellners: very limited. Basically an obsolete design best suited to f/15 refractors. 40 degree field of view. These days they're junk, and not made anymore.
If you want a 3-element eyepiece, buy a set of Edmund RKE's, they are as good as it gets with 3 elements.
The only other 3 element design on the market are the TMB supermonos, excellent planetary eyepieces (high contrast and sharp) but limited field of view.

Erfle: another very old design, better than Kellners; they give nice wide low-power field views in an f/8 scope, but no good in faster scopes, and no good at low focal lengths because the eye relief is very very short. So short that Erfles were never made much below 20mm focal length, and even at that size an orthoscopic was usually preferred. For a while I had a monster army-surplus 60mm Erfle, it needed a custom barrel as it was bigger than a 2" focusser, and the field of view was monstrous, BUT to be honest my 40mm TMB Paragon is a lot better in an f/7 refractor.

Most modern wideangle eyepieces will do a lot better than an Erfle - even the cheap GSO's, Orion Stratus, Baader Hyperion, Vixen LVW, TMB Paragon, TV Panoptic, Radian etc.

[kinetic]

John Bambury wrote a great little history of most types in
this post, part of a thread about Plössls (http://www.iceinspace.com.au/forum/showthread.php?t=19632).
http://www.iceinspace.com.au/forum/showpost.php?p=214230&postcount=6

FWIW the two cheap UO Kellners I have had for nearly 30 years perform
beautifully in my 8" F7 Homemade Newt. Shorter FL scopes, not so
well, as Wavy has said.