9 replies to this topic

[petmic]

When browsing through ZenMarket I came across a myserious looking eyepiece from Vixen.

 

 

It is marked as E.20mm and seems to have 36.4mm thread smiliar to Or32, K30 and K40 eyepieces. I found it is mentioned in Vixen catalogues from 1970s but mention of AFOV or optical formula.

 

I wonder does anyone recognize this eyepiece? 

 

https://zenmarket.jp...de=q1169255518 

[RebelScum]

Could it be an Erfle eyepiece?

[petmic]

Could it be an Erfle eyepiece?

Might be so. But then there also seems to be E13 and that would be a very short focal length for an Erfle design I guess.

[Bomber Bob]

Odd find...  Most of the Japanese makers sold these high FL eyepieces (usually Kellner) paired with an Extension for their "fast" Newtonians.  I've thought about buying a Mizar K40 version for my 130SL F5:   https://zenmarket.jp...ode=e1176884063

 

But I've also seen ASTRO, Carton, Kenko, Mizar, & Vixen versions.  They all have the standard 36.4mm thread.

 

The shortest ERFLE that I have is an old Jaegers 16mm with 1.25" barrel.  Love pairing it with my refractor RFTs...

Edited by Bomber Bob, 11 April 2025 - 11:44 AM.

[MisterDan]

It's a "Konig variant" (which means little ).

 

If I recall the schema correctly, it's 1-2-1 with the middle pair convex/concave (concave on the eye side). The singlets are both biconvex, but different (and unknown) radii.

 

Most Japan-made "Erfles" were not Erfles. "Erfle", unfortunately, became a generic "type" name for non-Smyth eyepieces with wide apparent fields.

 

If I run across the diagram (or any other info) I'm "sort'a recalling," I will follow up here.

 

Best wishes.

Dan

[petmic]

It's a "Konig variant" (which means little ).

Do you happen to know what would be the AFOV like?

[MisterDan]

I don't recall any indication of afov, so I don't know for sure.  I would presume its apparent field would be in the 55-60^o range. -Perhaps as much as ~62^o, but that's unlikely.

 

Best wishes.

[Jay_Reynolds_Freeman]

Might be so. But then there also seems to be E13 and that would be a very short focal length for an Erfle design I guess.

Not necessarily too short: Meade used to offer a 12.4 mm Research-Grade eyepiece that was marked and advertised as an Erfle.

 

Clear sky ...
 

[deSitter]

Might be so. But then there also seems to be E13 and that would be a very short focal length for an Erfle design I guess.

 

Actually not - e.g. the 1950s Questar came with a 25mm Kellner and a 10mm (I think) Erfle. They work well at long f/ratios.

 

-drl

[RichA]

Might be so. But then there also seems to be E13 and that would be a very short focal length for an Erfle design I guess.

Meade RG Erfles went down to 7mm.