7 replies to this topic

[Magnetic Field]

I am not using Kellners. No way people.

 

But interesting anyway.

 

I can only assume it is terrible at the outer field edge?

 

Given that Borg only produces/produced 'fast' refractors.

 

I came accross this in an old Borg Oasis catalogue from 2004.

 

[Simoes Pedro]

The question is always: "what is the F-ratio"?

 

Probably, also not a 1-2 Kellner.

[Avgvstvs]

Thanks Magnetic Fields what a wonderful time warp

 

17 years ago..average weight 40 grams

How much did they cost in 2004?

And why can't we buy them today?

I guess market forces have decided all these questions

 

In the 'good old days' I had a 25mm Kellner, 40mm Achromatic Huygens

and a 9 and 6mm Orthoscopics (these last 2 were Unitrons!) all in glorious 1 inch (or slightly less 0.945" me thinks)

I can't even remember seeing 1.25" yet

 

They seemed great at the time. But I can tell you that even a cheap set of standard

plossl's from todays beginner telescopes seem like Naglers by comparison.

And the views seemed great because I didn't know any better,

Al Nagler was probably still working for NASA

And my eyes were young with an 8" F7 mirror (how come no one makes these anymore!)

I enjoyed feeling young again and remember the drama's of hypered film

Let's do the time warp again!

[shaesavage]

I had the 13.5mm and it was not good in my f/7.5. Outer 40% was awful. Poor eye relief. They achieve the light weight because the entire body is plastic, no metal.  I should have tested the element to see if it was glass or plastic. I am a huge fan of Huygens, kellners, and orthos when they are of good quality. I would not recommend this eyepiece. 

[Magnetic Field]

I had the 13.5mm and it was not good in my f/7.5. Outer 40% was awful. Poor eye relief. They achieve the light weight because the entire body is plastic, no metal.  I should have tested the element to see if it was glass or plastic. I am a huge fan of Huygens, kellners, and orthos when they are of good quality. I would not recommend this eyepiece. 

Kind of crazy when you think of it.

 

Borg makes some very fine refractors made in Japan and then they  throw some plastic eyepieces into the mix.

 

 

Why wouldn't they include a bog standard Ploessl to the full telescope set.

 

Ploessls in 2004 were  not unheard of. They would have been solid performers. Although my Vixen NPL 25mm Ploessl doesn't work in my Borg 4" f6.4. The field in the Kellners then must even be worse.

Edited by Magnetic Field, 13 March 2021 - 11:32 AM.

[Magnetic Field]

The question is always: "what is the F-ratio"?

 

Probably, also not a 1-2 Kellner.

Borg makes and made refractors in the f4 (astro photography) to f7  (visual) range.

 

This then made me wonder if their Kellners represent some kind of improved modified Kellner (better field sharpness accross the field).

 

The Kellners often were part of their full set. Although my Borg ED D=101 f6.4 that I bought last year was not part of  a full set but in 2004 it also came also as full set with the Borg super Kellner 22mm.

 

By the way: a 25mm Vixen NPL Ploessl is literally useless (terrible field curvature) in my Borg that the reason why I ordered a TV DeLite.

 

Maybe the super wide Borg Kellners were an exact match for the lens design of the Borg 101 f6.4 ED.

Edited by Magnetic Field, 13 March 2021 - 11:34 AM.

[Magnetic Field]

Thanks Magnetic Fields what a wonderful time warp

 

17 years ago..average weight 40 grams

How much did they cost in 2004?

And why can't we buy them today?

I guess market forces have decided all these questions

 

In the 'good old days' I had a 25mm Kellner, 40mm Achromatic Huygens

and a 9 and 6mm Orthoscopics (these last 2 were Unitrons!) all in glorious 1 inch (or slightly less 0.945" me thinks)

I can't even remember seeing 1.25" yet

 

They seemed great at the time. But I can tell you that even a cheap set of standard

plossl's from todays beginner telescopes seem like Naglers by comparison.

And the views seemed great because I didn't know any better,

Al Nagler was probably still working for NASA

And my eyes were young with an 8" F7 mirror (how come no one makes these anymore!)

I enjoyed feeling young again and remember the drama's of hypered film

Let's do the time warp again!

Nostalgia.

 

Give us back those astro equipment catalogues from the 80s and 90s.

 

I remember my Vixen catalogue as a teenager. I sat there  in awe and thinking of all the great telescope developments coming out of Japan. Those men in white laboratory coats behind the telescope left an impression upon me.

[Simon B]

To be fair, these were very cheap in Japan when they came out, around $15

 

 

Apparently the 13.5mm has 5 elements in (3?) groups, the 22mm has 4 elements in 3 groups, and the 50mm has 2 elements in 2 groups

 

The 22 is called a kellner oddly, despite having 4 elements - traditional kellners only have 3 elements

 

 

Also there seems to be a mistake in that Borg ad, the 13.5 is supposed to say 64° AFOV, and the 22 should say 70°, instead of the other way around