Eyepiece ID sought

[lsintampa]

I acquired some eyepieces from a recent used AVX mount purchase. For the most part all of the EP's are easily identified except for one.

The EP itself (no barrel) is marked as Celestron K.40mm

The barrel piece is marked Japan - circle T and has it's own glass component.

Any idea what this is?

[notFritzArgelander]

It's likely a Celestron branded 40mm Kellner eyepiece made by Tani in Japan.

[lsintampa]

It's likely a Celestron branded 40mm Kellner eyepiece made by Tani in Japan.

What I'm curious about is the what the barrel is.... all my EP barrels don't have any lens in them... so it's the barrel I'm most curious about.

[Lady Fraktor]

Could you post a picture or two?

[Ruud]

Here's a wikipedia image of the Kellner design.

To the left is the field lens, the doublet to the right is the eye lens

The arrow indicates the direction of the light.

There is also a field stop which limits the field of view to the region that the eyepiece can show without blur.

[Lady Fraktor]

You may find the Kellner not a great eyepiece even at f/10, they are prone to lateral colour and ghosting when viewing brighter objects.
At f/15 they do a reasonable job for planetary/ lunar other than the ghosting potential.

[notFritzArgelander]

It's likely a Celestron branded 40mm Kellner eyepiece made by Tani in Japan.

What I'm curious about is the what the barrel is.... all my EP barrels don't have any lens in them... so it's the barrel I'm most curious about.

It's likely the field stop and field lens. It is not completely unheard of to find optics in the barrel. Rare, but not impossible. Post a pic?

[lsintampa]

Could you post a picture or two?

here ya go....

I see the diagram for k ep's but what would the point be for the field lens (if that is what it is) to be in the barrel, which is removable.... can that barrel be use on other ep's

[notFritzArgelander]

Could you post a picture or two?

here ya go....

I see the diagram for k ep's but what would the point be for the field lens (if that is what it is) to be in the barrel, which is removable.... can that barrel be use on other ep's

The point of it would be to have the optics fit the mechanical design for the eyepiece. If you didn't put the field lens in the barrel the EP would have to be longer to have proper spacing between field and eye lens assemblies.

Not really interchangeable with other eyepieces.....

[lsintampa]

Could you post a picture or two?

here ya go....

I see the diagram for k ep's but what would the point be for the field lens (if that is what it is) to be in the barrel, which is removable.... can that barrel be use on other ep's

The point of it would be to have the optics fit the mechanical design for the eyepiece. If you didn't put the field lens in the barrel the EP would have to be longer to have proper spacing between field and eye lens assemblies.

Not really interchangeable with other eyepieces.....

So what if I used an "empty" barrel????

I'm trying to figure out what the field lens does. At first I thought it might be a barrow barrel.

I'm just a novice - but this is the first time I saw a lens in a barrel...

[lsintampa]

some more digging about and it seems that is just how they were made .... so my guess is it's just a 40mm kellner

[Lady Fraktor]

Definitely a 40mm Kellner and no the will not work (properly) without the lens.
At f/12 and slower a well made Kellner will put up a view comparable to a good Symmetrical/ Plossl but there are not a lot of refractors in the longer focal lengths anymore.

[Piet Le Roux]

I have a cheap 40mm 2" Kellner distributed by Astromania : it is not great and does not have flat focus form edge to edge but its very bright, if I am trying to find a big and dim deep sky object with my F10 SCT, this is what I use. It also has a lens halfway down the barrel.