Unusual find: Abbe-Koenig prisms on Orion binos!

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DozerBolt
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Unusual find: Abbe-Koenig prisms on Orion binos!

#1

Post by DozerBolt »


Greetings,
I had this discussion on another site, but it was so fascinating I wanted to share it here.

Abbe-Koenig roof prisms are weird, and expensive - they have long prism elements in a sort of "boomerang" layout, and they are famous for (contrary to common knowledge) being high light transmission roofs. Historically they were only used in large primary, low light applications, like 9x63 or 8x56. And there are only a small number of builders who make these, mostly European - Zeiss, Docter, Zwarovski, Optolyth. Nikon make a set - the 7x50 WX, all yours for only $6000 dollars! Yikes.

Enter: my Orion 9x63 roof prisms! In 1991 I purchased the last pair on clearance at my local Orion dealer - 9x63 roofs! Everybody knows that won't work, right? Still, they were/are super cool, and nobody has a pair like them. Then, this weekend, I learned about Abbe-Koenig roof prisms on another site...

Now, for the record, I am 99% convinced that my Orion Mini-Giant 9x63 roof prisms are Abbe-Koenig prisms! Here's why: upon analysis, a telltale sign of AK prisms is that, due to their design, they are "bow-legged", i.e. the primaries are not in the same plane as the eyepieces. Standard SP roof prisms (which are overwhelmingly common BTW) are essentially perfectly straight tubes between the primaries and the eyepieces.

There IS one example of AKs being "straight" - the Nikon WX's, which are $6000+ (!) and are probably a unique/ tailored design (you can see the schematics online); virtually all other AK prisms have the "bow legged" bend when you study them.

In particular, the Orions appear to be a direct Japanese knockoff of the Optolyth 9x63's - virtual dead ringers. The only differences appear to be (1) my pair have green coatings, whereas the Optolyth's have scarlet/purple coatings; and (2) the mystery Japanese builders moved the neckstrap anchors from the side to the back.

BTW I love these! They are cool, unique, have super long eye relief, a strangely large apparent FOV (even though their true field is listed as 5.5 degrees), kind of a "porthole" feeling, and have always been very bright, despite the common wisdom around roofs; perhaps AK is why! The weight even makes them very steady in the hand and oddly easy to use; they feel narrower than one would expect in the field. They've always been an interesting addition to my collection - but I use 'em all the time!

I took these with me when traveling to Australia, to observe the Southern skies, as they were the biggest optics to fit in my luggage. I can also say they are RUGGED (another attribute of roofs); these are in perfect shape, but I have used them and knocked them around in my travels. And NO, you can't have 'em! ;-)
Attachments
Orion 9x63 roofs green coatings.jpg
Orion 9x63 roofs top.jpg
Orion 9x63 roofs front long.jpg
Optolyth 9x63 w AK roof prisms.jpg
DozerBolt from Northern California
Odyssey 8" Dob, Dynamax 6" Cat, Orion Shortube 90mm, Restored Tasco 9F 60mm, Meade EclipseView 82mm tabletop;
Orion 9x63 Little Giant AK roofs, Orion Ultra 2x54 Galilleans, Vortex Crossfire HD 12x50 roofs, Nikon Owl II 7x50, Atlas Eagle Owl 10x50 Porros;
Swift Audubon 8.5x44 804b(2), 10x42 Orion Otter ED SP Roofs, more;
"My other telescopes are Hubble and Spitzer"
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Re: Unusual find: Abbe-Koenig prisms on Orion binos!

#2

Post by DozerBolt »


FYI here's a picture of the Abbe-Koenig (AK) and Schmidt-Pachan (SP) roof designs;
Virtually every roof prism binocular today is SP. However, roofs get their rep from the fact that SP prisms reflect/redirect 6 times before exiting; I believe there is also a lightwave phase issue with SP's, which is why phase correction is so critical for SP roofs. I don't understand it well enough to know whether the same applies to AK prisms.

Notice that AKs only redirect 4x - that's even less than standard Porro prisms! (5x)
AK is really an elegant binocular prism design.
Attachments
Roof prism types.jpg
Last edited by DozerBolt on Sun May 17, 2020 4:24 am, edited 1 time in total.
DozerBolt from Northern California
Odyssey 8" Dob, Dynamax 6" Cat, Orion Shortube 90mm, Restored Tasco 9F 60mm, Meade EclipseView 82mm tabletop;
Orion 9x63 Little Giant AK roofs, Orion Ultra 2x54 Galilleans, Vortex Crossfire HD 12x50 roofs, Nikon Owl II 7x50, Atlas Eagle Owl 10x50 Porros;
Swift Audubon 8.5x44 804b(2), 10x42 Orion Otter ED SP Roofs, more;
"My other telescopes are Hubble and Spitzer"
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Ylem United States of America
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Re: Unusual find: Abbe-Koenig prisms on Orion binos!

#3

Post by Ylem »


Thanks for posting that info :)
I love my Orion 9x63 :)
Yes, made in Japan ;)
Clear Skies,
-Jeff :telescopewink:


Member; ASTRA-NJ



Orion 80ED
Celestron C5, 6SE, Celestar 8
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Re: Unusual find: Abbe-Koenig prisms on Orion binos!

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Post by helicon »


Very interesting and glad you have such a nice pair of seemingly rare binos.
-Michael
Refractors: ES AR152 f/6.5 Achromat on Twilight II, Celestron 102mm XLT f/9.8 on Celestron Heavy Duty Alt Az mount, KOWA 90mm spotting scope
Binoculars: Celestron SkyMaster 15x70, Bushnell 10x50
Eyepieces: Various, GSO Superview, 9mm Plossl, Celestron 25mm Plossl
Camera: ZWO ASI 120
Naked Eye: Two Eyeballs
Latitude: 48.7229° N
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j.gardavsky Germany
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Re: Unusual find: Abbe-Koenig prisms on Orion binos!

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Post by j.gardavsky »


Hello Dozert,

and congratulations on the binos! In such a good condition they are not often seen.
Best,
JG
6" F/5 Sky-Watcher achro, 2" BBHS Star Diagonal, 2" zenith prism, 1.25" Takahashi prism
Leica 82mm APO Televid
Eyepieces: Docter UWA; Leica B WW and WW Asph. Zoom; Leica HC Plan S and L, monocentric; Pentax SMC XW, O-, XO; Tak MC O, Carl Zeiss B WW, and Pl, E-Pl, S-Pl, W-Pl;
Swarovski SW; Baader Symmetric Diascope Edition; Nikon NAV SW, ; TMB supermonocentric; Rodenstock; Vixen HR; TV Delos
Filters: Astrodon, Astronomik, Baader, Balzers, Zeiss West and East, Lumicon
Binoculars (7x42 up to 15x85): Docter Nobilem, Leica Ultravid, Nikon Astroluxe, Swarovski EL Swarovision; BA8 (Kunming Optical)
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Re: Unusual find: Abbe-Koenig prisms on Orion binos!

#6

Post by DozerBolt »


Thanks J! I like to look at my fine optics (binoculars and telescopes) as less of an owner and more of a steward;
I super enjoy them, and I hope one day another lucky owner can enjoy them like I have when I'm done (but not yet!)
Although I gotta say, 30 year sure the heck flew by! Although in astronomical terms, I suppose it's still just the blink of an eye...
DozerBolt from Northern California
Odyssey 8" Dob, Dynamax 6" Cat, Orion Shortube 90mm, Restored Tasco 9F 60mm, Meade EclipseView 82mm tabletop;
Orion 9x63 Little Giant AK roofs, Orion Ultra 2x54 Galilleans, Vortex Crossfire HD 12x50 roofs, Nikon Owl II 7x50, Atlas Eagle Owl 10x50 Porros;
Swift Audubon 8.5x44 804b(2), 10x42 Orion Otter ED SP Roofs, more;
"My other telescopes are Hubble and Spitzer"
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