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A "Practical" Planetary Eyepiece?

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#101 Steve Cox

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Posted 06 June 2020 - 07:20 AM

This begs the question how much more comfortable would the 8mm TV Plössl have been, had it been re-housed into a volcano-top design.

 

 

Clear skies!
Thomas, Denmark

I agree. When I had mine, I usually removed the eye eyecup to observe and that made it much more comfortable, in addition to not fogging over as much.



#102 BillP

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Posted 06 June 2020 - 08:40 AM

Tele Vue Plossls *are* better than vanilla ones if you consider field astigmatism to be a problem. They are actually patented for exactly this but as a consequence they are no longer orthoscopic.

https://patents.goog...&oq="Tele vue"

The patent design also tightens the eye relief from the standard Plossl.  And, as mentioned by Don, the design also limits the lens size so consequently some of the focal lengths will vignette with Barlow and they need a telecentric instead (i.e., Powermate).  So "better" is really quite subjective.  My instruments are f/8.  Off-axis is just fine with any Plossl or Abbe.  If anything, it can be seen as tailored more for the fast Dob market with so much concern for the off-axis at fast focal ratios.  In addition, quite a number of Plossls now have a similar prescription with concave eye and field lenses.  So the field of Plossls that are not "vanilla" ones extends to much more than just TV.


Edited by BillP, 06 June 2020 - 08:41 AM.

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#103 lylver

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Posted 06 June 2020 - 08:42 AM

/.../

 

There is a specific bit of text at the TV site...

Al Nagler thought that a nice Plossl with high-index glass

    could best the Abbe with less fuss.  So...the TV Plossl

    is the chosen competitor to the ortho.

Yes may be, but in this case you should consider Brandon eyepiece that use heavier crown glass (lanthanum), has higher eye relief. I published estimated datas in ATM DIY forum section.

or Tal new super-plössl that use (I think) the lightest, unique, LZOS lanthanum crown : CTK3 (nd=1.659 vd=57.36) combined with one of the strongest flint : SF6 (russian version ТФ10 nd=1.806 vd=25.37).

 

TV plössl use SSK5 (nd=1.658 vd 50.88) and SF19(nd=1.667 vd=33.12)

 

They have same edge correction but when you look at medium field, chromatism is much better handled in the TAL (left)

10mm fl simulation @f/10, color range 422->664

TAL & TV

For historical comparison.

The old asymetricals : Brandon (1943, violet is 422nm : uncorrected) & Clavé (~1950, this version has negative coma)

TAL10.jpg TV10.JPG BRD10.jpg CLV10.jpg

Best polystrehl ? I let you guess.

Note : eyepieces spots are shown with field curvature canceled.


Edited by lylver, 06 June 2020 - 06:49 PM.

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#104 jeffmac

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Posted 06 June 2020 - 09:38 AM

This begs the question how much more comfortable would the 8mm TV Plössl have been, had it been re-housed into a volcano-top design.

 

 

Clear skies!
Thomas, Denmark

 

 

Yes, indeed. Of course, I could be happy with a good 8mm Abbe VT, if they were available. Comfortable four element glass in the 8mm focal length is rarer than hen's teeth.


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#105 Jeff Morgan

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Posted 06 June 2020 - 09:47 AM

Amen to that.  I have to dodge the problem with a focal extender,

but a few Plossls have been happily converted to 'mesa' here.

(you look right into the glass stack, with not even the dip of the 'volcano').

 

https://www.youtube....h?v=qgjPa5JkecA



#106 jeffmac

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Posted 06 June 2020 - 09:47 AM

Yes may be, but in this case you should consider Brandon eyepiece that use heavier crown glass (lanthanum), has higher eye relief. I published estimated datas in ATM DIY forum section.
or Tal new super-plössl that use (I think) the lightest, unique, LZOS lanthanum crown : CTK3 (nd=1.659 vd=57.36) combined with one of the strongest flint : SF6 (russian version ТФ10 nd=1.806 vd=25.37).
 
TV plössl use SSK5 (nd=1.658 vd 50.88) and SF19(nd=1.667 vd=33.12)
 
They have same edge correction but when you look at medium field, chromatism is much better handled in the TAL (left)
10mm fl simulation @f/10, color range 422->664
TAL & TV
attachicon.gif10TAL.JPGattachicon.gifTV10.JPG
For historical comparison.
The old asymetricals : Brandon (1943) & Clavé (~1950)
attachicon.gif10BRD.JPGattachicon.gif10CLV.JPG
Best polystrehl ? I let you guess. I can magnify...


I've heard some good things about the 8mm Brandon, but the eye relief is not one of those things. I must confess though, I've never tried one. If I ever acquired one, it would have to be flat top model.

#107 jeffmac

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Posted 06 June 2020 - 11:18 AM

Amen to that.  I have to dodge the problem with a focal extender,

but a few Plossls have been happily converted to 'mesa' here.

(you look right into the glass stack, with not even the dip of the 'volcano').

 

attachicon.gifDSC_0015.JPG

 

    (after the E6000 tacking is solid, black "puffy paint" is used

       to coat the stack, to giving blackening and strength at the same time)

 

We go from annoying and blurred to comfortable and sharp..

  ..it parts the eyelashes well.

Granted, a volcano top would be far more rugged and

    civilized for the TV.

 

 

There is a specific bit of text at the TV site...

Al Nagler thought that a nice Plossl with high-index glass

    could best the Abbe with less fuss.  So...the TV Plossl

    is the chosen competitor to the ortho.

 

Martin, you are an eyepiece "mad scientist".  lol.gif


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#108 lylver

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Posted 06 June 2020 - 12:43 PM

I've heard some good things about the 8mm Brandon, but the eye relief is not one of those things. I must confess though, I've never tried one. If I ever acquired one, it would have to be flat top model.

I agree there is an eye relief problem with Brandon due to construction.

The 12 mm I have is comfortable with eye doublet big enough, but eye positionning is not guided. Cell is thick, diameter is big for the eye. Another top of cell would be much better. I initially planned to get the 8 but I abandonned as I did for the TV plössl.

1"1/4 cells are too big for me. Old 0.965" eyepieces work better for me except Pentax ortho 7mm I found uncomfortable either (big flat top). A morphology issue for me.
 



#109 Astrojensen

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Posted 06 June 2020 - 02:01 PM

Speaking of eye relief and comfort, this made me think of an eyepiece I have:

 

gallery_55742_4772_15945.jpg

 

And described in detail in: https://www.cloudyni...epiece-sort-of/

 

Today, I compared it in a binoviewer with a 10mm Zeiss Jena ortho and their magnifications are identical, so it's a 10mm and not a 10.5mm, as I originally guessed. 

 

But here's the interesting thing: This eyepiece is MUCH more comfortable than the 10mm Zeiss ortho or a 9mm VT ortho. It's as comfortable, more or less, as a 12.5mm UO VT ortho. It's also far more comfortable than a 10mm Plössl. And it has a wider apparent field than any of them, around 55°. 

 

But the real shocker was that it's also SHARPER and BRIGHTER than the 10mm Zeiss Jena ortho in a direct comparison last night on Mu Bootis. The dim double companion (it's a triple star) was definitely easier to split in the 10mm König, than in the 10mm Zeiss! I did multiple swaps and the result was always the same. Sadly, clouds rolled in, before I could do some more comparisons.  

 

Even more shocking is that the entire binocular that the 10mm König comes from cost HALF of what a single 10mm Zeiss Jena ortho did, when they were still produced. And the König is a better planetary eyepiece (at least on-axis). That makes absolutely no sense whatsoever, in light of recent claims that superpolished eyepieces are more expensive than others.   

 

Off-axis, the König is showing some field curvature and astigmatism is starting to get a bit apparent near the edge, but in general use on my f/13 refractor, stars are quite tight over most of the field and performance is very pleasing. The center is absolutely dead sharp. I need to see how it performs at f/8 and at shorter focal lengths. 

 

Now, I need to do more testing on several different telescopes, but my gut feeling is that this design should work eminently well down to at least f/8. Given how very comfortable it feels at 10mm, I'd say that this should work eminently well down to 4mm, just like an ortho. Given that it avoids the problematic triplet of the Abbe ortho and has much better eye relief than the symmetrical Plössl, I think the König should be given some serious consideration in a dedicated planetary eyepiece line. 

 

 

Clear skies!
Thomas, Denmark


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#110 lylver

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Posted 07 June 2020 - 04:49 AM

Yes Thomas, you are right, König 2-1 is a good planetary eyepieces since his early version, but the useable field is originally narrower, not really efficient on extended view like Moon. Eye relief is ~1.07f. Nice orthoscopy (<5% on field).

The design is from @Vla on his site 10mm f/10. It already use some high indexes glass (SK2, SK10, SF4) so hard to enhance. This one has only 37° AFOV due ... to high eye relief.

The three glass design makes it better than the RKE (Edmund) for central chromatism.

Thomas Back already evaluated this when he designed the TMB planetary. He needed to adjust the chromatism and spherical aberration to extend the angle and permit low f/D use. Air-spaced barlow was so mandatory.

Note for RKE : at 71% field focused as Edmund specifies (tricky to do and needs top quality manufacturing). As you can see RKE is a off-axis use° eyepiece (Clavé too... but I only estimated the design : Chris Lord is a specialist ot it)

KO2-10s.jpg RKE-10s.jpg

Maximal off-axis angle is around the 12.5° as I stated upper, due to eye rotation degradation (cornea astigmatism etc...). Official organisation like CIE uses this (2° and 10° angle) as reference.


Edited by lylver, 07 June 2020 - 07:55 AM.


#111 MartinPond

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Posted 07 June 2020 - 09:46 AM

One of my favorites, the 8x21-pillaged 

  (eye) 1 , 2 (objective)    Konig.

  or as others put it,

    (objective)      2 , 1  (eye)

 

Most are very good, many are excellent!

A warning :

   ---nowadays, the cheaper 8x21s have a 

       1,1 plastic Ramsden     (you can see  50% sorta sharp of 60 degrees)

   ---plenty of older or more expensive 8x21s are available, though.

   They often show up, dirty, cheap, at flea markets.

   Rural hunters toss them around, or they get cooked and greasy.

   Since 8x21s are packed with lots of grease, restoration is 

     too much trouble, but pillaging is easy.

     Still a fantastic planetary, with the right mounting.



#112 MartinPond

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Posted 07 June 2020 - 09:50 AM

Martin, you are an eyepiece "mad scientist".  lol.gif

Or "Mad Max"?  

I call that 'Road Warrior construction'.

 

It's the best in the world for eyelash deflection..


Edited by MartinPond, 07 June 2020 - 09:51 AM.

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#113 MartinPond

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Posted 07 June 2020 - 09:53 AM

Yes may be, but in this case you should consider Brandon eyepiece that use heavier crown glass (lanthanum), has higher eye relief. I published estimated datas in ATM DIY forum section.

or Tal new super-plössl that use (I think) the lightest, unique, LZOS lanthanum crown : CTK3 (nd=1.659 vd=57.36) combined with one of the strongest flint : SF6 (russian version ТФ10 nd=1.806 vd=25.37).

 

TV plössl use SSK5 (nd=1.658 vd 50.88) and SF19(nd=1.667 vd=33.12)

 

They have same edge correction but when you look at medium field, chromatism is much better handled in the TAL (left)

10mm fl simulation @f/10, color range 422->664

TAL & TV

For historical comparison.

The old asymetricals : Brandon (1943, violet is 422nm : uncorrected) & Clavé (~1950, this version has negative coma)

attachicon.gifTAL10.jpg attachicon.gifTV10.JPG attachicon.gifBRD10.jpg attachicon.gifCLV10.jpg

Best polystrehl ? I let you guess.

Note : eyepieces spots are shown with field curvature canceled.

 

I am amazed at how much alike all these are, despite all the fussing.

Thanks for the fascinating diagrams!



#114 jeffmac

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Posted 07 June 2020 - 01:52 PM


What were some of the shorter Konig focal lengths that were manufactured and by who? Since I got into the hobby some 25 years ago, all I remember were medium (15mm, 25mm) to long (30mm, 40mm) focal lengths. Those were University Optics branded. Come to think of it, I think I remember a UO 10mm as well.

#115 Astrojensen

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Posted 07 June 2020 - 03:56 PM

I've seen UO Königs down to 8mm, but maybe there were also shorter ones. My late friend and mentor Per Darnell had quite a few of them. I remember at least 8mm and 12mm. They were VERY sharp, from what I recall.

 

 

Clear skies!
Thomas, Denmark


Edited by Astrojensen, 07 June 2020 - 04:03 PM.


#116 BillP

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Posted 07 June 2020 - 04:22 PM

UO Konigs in 1.25" were: 6.5, 8, 12, 16, 24, 32.

 

In 2" Standard they had 32, 40, then in the 2" MK70/80 series 25, 32, 40.

 

https://www.cloudyni...-1511018090.jpg


Edited by BillP, 07 June 2020 - 04:26 PM.

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#117 Starman1

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Posted 08 June 2020 - 12:10 PM

König, though, designed many eyepieces.

The most commonly ray-traced is the 3 element 1:2 design, but the UO Königs sold in the '80s were, IIRC, the 1:2:1 design.

And i cannot recall the exact configuration of their "König-II" series.

So there is not just one "König" eyepiece.


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#118 BillP

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Posted 08 June 2020 - 01:26 PM

Perhaps a 2-1-1 ...

 

https://www.cloudyni...lery/?p=3779505

 

https://www.cloudyni...lery/?p=3781182

 

But then Bill Rose found they were both 1-2-1, with the Konig II having better coatings and blackened edges ...

 

https://www.cloudyni...mbly/?p=2691891


Edited by BillP, 08 June 2020 - 01:26 PM.

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#119 lylver

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Posted 08 June 2020 - 03:11 PM

My 16mm König II from University Optics : 1-2-1 design. Glasses seems heavier than mean weight of other eyepieces I use to dismount, only a feeling.

Lenses diameter 16.5mm eye (asymetric biconvex, eye side long radius, internal stronger), 21mm doublet (slight concave towards eye, short radius convex for field, thick, buried curvature seems strong) , 22.5mm field (asymetric biconvex, stronger internal curvature), field stop is around 18mm and quite near the lens, around 1cm.

A complex eyepiece, that has between 60-64° AFOV, ring was one drop glued (acetone dissolves it)

The internal cell is not metal and there is some mat paint : fine finished. Not a planetary but center is nicely sharp, a pleasure, more comfortable with a barlow on Moon and without addition a keeper eyepiece on my achromat f/12.5

Not identical to Meade RG WA 20mm I had.

IMG_20200608_213121.jpg


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#120 jeffmac

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Posted 08 June 2020 - 07:30 PM

The Konigs must have a number of fans. I just did a search in CN classifieds and they don't appear to come up for sale all that often, at least in the shorter focal lengths.



#121 MartinPond

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Posted 09 June 2020 - 04:46 AM

König, though, designed many eyepieces.

The most commonly ray-traced is the 3 element 1:2 design, but the UO Königs sold in the '80s were, IIRC, the 1:2:1 design.

And i cannot recall the exact configuration of their "König-II" series.

So there is not just one "König" eyepiece.

 

Konig-II  is usually 1,1,2 .  Not as wide field as the 1,2,1 , 

    but wider than the 1,2 and very easy eye placement.

    Often has a meniscus before the eye. It's common in the

    the premium Bushnell "Custom" binocular line.

 

The 1,2,1 has some inherebt reduced contrast, but I imagine

 it benefitted a lot from multicoating.

 

The Nikon spotter LERs and one of the Russell RGs with long eye relief 

   both had a 50-deg field and seem to achieve the longer eye relief

   via a strong objective-facing dimple on a long 1,2-Konig. 

    (inboard Barlow, sort of).

   That also improves the field edges.  I call that 1,2,(-1)


Edited by MartinPond, 09 June 2020 - 04:52 AM.


#122 luxo II

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Posted 09 June 2020 - 06:14 AM

The Konigs must have a number of fans. I just did a search in CN classifieds and they don't appear to come up for sale all that often, at least in the shorter focal lengths.

They don't come up for sale for good reason - few were sold and they weren't all that great. There are quite a few other rare eyepieces such as the Pretoria that likewise you won't find now - for good reason - they were nothing special even then.

 

In the 80's the UO Konigs were only available in 2, maybe 3 focal lengths and not short - I recall having a 16mm and one around 20-24mm. They were 1,2,1 construction.

 

IMHO not all that good either - I was using an SCT at the time - at the short end RKE, orthos, and plossls were preferable, and at the long end Kellners were distinctly better. Vixen released the LV range which pretty much killed off the cheap stuff and Televue dominated the top end much as they do now.

 

After a couple of years mine went where they belonged - in the bin - out of disgust. I didn't have the heart to give them to a noob who didn't know any better, knowing he'd figure out they were crap.


Edited by luxo II, 09 June 2020 - 06:26 AM.

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#123 j.gardavsky

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Posted 09 June 2020 - 07:19 AM

The (field stop - 2 - 1) f=25mm König can be still found at Zeiss as the E-Pl (extra planar) eyepiece with one aspheric surface, it has been manufactured by Leica as the Leica HC Plan f=25mm, and is still manufactured as the Leica L Plan (f=25mm, f=32mm) with the Leica proprietary glass materials - different from Schott. All lenses are multicoated.

 

These EPs offer an enormous contrast and high transmissivity, which can be hardly beaten,

 

https://www.cloudyni...plan-eyepieces/

 

https://www.cloudyni...my-microscopes/

 

These eyepieces are sized for the 30mm metric insert in the microscope binoviewers.

 

I don't have any planetary telescope, and take them for the faintest and most difficult large DSOs.

 

Best,

JG



#124 luxo II

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Posted 09 June 2020 - 08:16 AM

Off-axis they were Orr-ful. Which is much worse than Er-full. Even in a planetary telescope (and I have had a few).

Note the pronunciation !

 

As for "hardly can be beaten", well yes they can, by virtually any modern eyepiece with multicoatings - and also by a simple spherical ball eyepiece (1 element, yes really, one and only 1 element).


Edited by luxo II, 09 June 2020 - 08:21 AM.


#125 Astrojensen

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Posted 09 June 2020 - 10:15 AM

Off-axis they were Orr-ful. Which is much worse than Er-full. Even in a planetary telescope (and I have had a few).

Note the pronunciation !

 

As for "hardly can be beaten", well yes they can, by virtually any modern eyepiece with multicoatings - and also by a simple spherical ball eyepiece (1 element, yes really, one and only 1 element).

Erm, do you know what you're talking about? These ARE modern eyepieces, in the sense that they use very advanced glasses and coating technologies, even if their designs are simple. 

 

We're not talking about any old Kellner here, mind you, but extreme high-end, very expensive eyepieces from some of the top optical manufacturers in the world, if not THE top. Gardavsky wasn't talking about the UO Königs, but Königs from Zeiss and Leica. There's a bit of a difference there... 

 

 

Clear skies!
Thomas, Denmark


Edited by Astrojensen, 09 June 2020 - 10:17 AM.

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