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Michalis S
member
Reged: 06/07/05
Posts: 38
Loc: Greece, Athens
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Hello,
Recently I got the idea of bying binoculars.
I saw the TS 20x80 - Triplet Objective. Does anybody has any reviews about them?
I'm willing to spend no more than 250 euros.. Any other suggestions?
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Orion Optics (UK) 10¨ Dob,labda/6, Hilux coatings
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12783
Loc: Cumberland, R I , USA42N71.4W
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Quote:
I saw the TS 20x80 - Triplet Objective. Does anybody has any reviews about them?
See Mini Reviews on
Oberwerk 20x80 Deluxe II
Garret Optical 20x80 Gemini
CN Reports - Binoculars on
Binocular Tets and Comparisons
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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Glassthrower
Vendor - Galactic Stone & Ironworks
Reged: 04/07/05
Posts: 14992
Loc: Kuiper Belt
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Michalis' query has given good opportunity to touch on something I am still unclear about when it comes to these triplet binocular objectives : color correction and performance.
1) Are these triplet 20x80's any sharper across the field than the standard doublet 20x80?
2) Is the triplet better color corrected?
3) Do the 20x80 triplets offered by Obie, GO, and others have a shorter f/l than the standard 20x80? I seem to recall reading somewhere that the triplet has a slightly-shorter focal length - perhaps cancelling out any CA benefit from the triplet objectives.
A triplet objective in a refractor is usually associated with an APO or semi-APO system.....but what exactly does it mean in a binocular?
Clear dark skies...
MikeG
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Michael Gilmer - Member of the Meteoritical Society & Collector of Falling Stars.
Galactic Stone & Ironworks - Specializing in exotic and rare meteorite falls.
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Joad
Wordsmith
Reged: 03/22/05
Posts: 12022
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Can't answer all your questions, GT, but I think I can answer the color correction one. A true APO needs a special ED glass of some sort , so an APO can be a doublet if it has that glass, but a triplet with ED glass included in the elements offers even more color suppression (if it is designed and constructed well, of course). Where there is no special ED glass, there isn't a true APO, but the well made and well designed triplets out there (like the Oberwerk 100mm BTs) offer semi-APO performance that is not a mere advertising term. Semi-APO, in practice (I am not offering a technical definition, though there is one), provides a higher level of achromatic CA suppression than does an ordinary achromat. The triplets are also a lot heavier, though.
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12783
Loc: Cumberland, R I , USA42N71.4W
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Quote:
A true APO needs a special ED glass of some sort , so an APO can be a doublet if it has that glass, but a triplet with ED glass included in the elements offers even more color suppression (if it is designed and constructed well, of course). Where there is no special ED glass, there isn't a true APO, but the well made and well designed triplets out there (like the Oberwerk 100mm BTs) offer semi-APO performance that is not a mere advertising term. Semi-APO, in practice (I am not offering a technical definition, though there is one), provides a higher level of achromatic CA suppression than does an ordinary achromat. The triplets are also a lot heavier, though.
An Apochromatic lens system is any that can produce color correction to 1:8000 of focal length. A semi-apo is generally accepted as 1:4000.
An achromat is generally about 1:1800 to 1:2000.
My TV85 is an APO. It is a doublet. It is produce from special dispersion glass.
Quote:
Do the 20x80 triplets offered by Obie, GO, and others have a shorter f/l than the standard 20x80? I seem to recall reading somewhere that the triplet has a slightly-shorter focal length - perhaps cancelling out any CA benefit from the triplet objectives.
A triplet objective in a refractor is usually associated with an APO or semi-APO system.....but what exactly does it mean in a binocular?
Don't be confused that triplet signifies Apo or even semi-Apo. Also don't be confused that it takes a triplet to achieve that. A triplet can still be an achromat if it does not achieve much more than 1:2000 correction. A doublet can be semi-apo if it achieves 1:4000 correction and it can be an Apo if it achieves 1:8000.
As regards focal length, ?shorter than what standard?, the Oberwerk Standard (by model name), or all other standard 20x80 binoculars? They are all shorter than the Oberwerk Standard, that was a very long F binocular. But once again, don't be confused that binoculars in this range will or will not cancel out CA. These are all very fast, mostly approx f/4, maybe f/4.5. There is a tremendous amount of CA inherent in such fast optics. Making it a triplet does not necessarily make it a semi-apo. Correcting it to 1:4000 makes it a semi-apo.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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Glassthrower
Vendor - Galactic Stone & Ironworks
Reged: 04/07/05
Posts: 14992
Loc: Kuiper Belt
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Thanks for the clarification on APO/Semi-APO and doublet/triplet. I guess what I am really asking here is this : Does the Obie or GO 20x80 triplet "perform" any better than a doublet 20x80? Why the extra glass? If the extra element(s) do nothing more than contribute weight, then why use them? Is there some benefit in this particular application? Has anyone looked through a 20x80 triplet and compared it to a 20x80 doublet of similar vintage? Any noticeable difference in the view for the extra weight of two additional elements?
Clear dark skies...
MikeG
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Michael Gilmer - Member of the Meteoritical Society & Collector of Falling Stars.
Galactic Stone & Ironworks - Specializing in exotic and rare meteorite falls.
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12783
Loc: Cumberland, R I , USA42N71.4W
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Quote:
I guess what I am really asking here is this : Does the Obie or GO 20x80 triplet "perform" any better than a doublet 20x80? Why the extra glass? If the extra element(s) do nothing more than contribute weight, then why use them? Is there some benefit in this particular application? Has anyone looked through a 20x80 triplet and compared it to a 20x80 doublet of similar vintage? Any noticeable difference in the view for the extra weight of two additional elements?
MikeG
Well 1st,
If you find a company that is distributing a binocular with an extra element that does nothing more than contribute weight, avoid that company.
2nd,
The third element is there to contribute additional degrees of freedom in lens design. Hopefully the design improves color correction.
3rd
Don't assume all doublets are the same, they are not.
Finally,
I guess the best I could do is point you to all my CN Reviews and CN Reports. In them you can find probably 3 or 4 different 20x80s. Cut to the chase and just read the sections on CA, if CA is all you are concerned about.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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milt
sage
Reged: 09/13/04
Posts: 440
Loc: Arizona
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Quote:
An achromat is generally about 1:1800 to 1:2000.
This is what the vast majority of binoculars are.
For those coming up to speed on this topic, what Ed means is that the focal length for red and blue is about 1.0005 times the focal length of green, or one part in 2000 longer. Thus when green is perfectly focused red & blue are slightly defocused, creating the halo that we see in high power achromatic binoculars. The closer together we can bring the focal lengths of the visible colors, the less fringing we will see.
However, there are other problems that can degrade the view more than a little color fringing. Spherical aberration makes it impossible to achieve a pinpoint star, astigmatism turns it into a cross and coma creates comets around the field edges. I would personally rather have a well-figured achromatic doublet than a poorly-figured triplet any day.
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Clear skies, Milt
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Glassthrower
Vendor - Galactic Stone & Ironworks
Reged: 04/07/05
Posts: 14992
Loc: Kuiper Belt
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Quote:
Well 1st,
If you find a company that is distributing a binocular with an extra element that does nothing more than contribute weight, avoid that company.
I would assume that Oberwerk and Garrett Optical are NOT companies that would offer a design with a useless extra element in it. The fact that Obie and GO offer this binocular leads me to believe that the extra element must do something positive in terms of performance. Little is said or claimed on either vendor site regarding the exact nature and purpose of the third element. It leaves me curious.
Quote:
2nd,
The third element is there to contribute additional degrees of freedom in lens design. Hopefully the design improves color correction.
Does this mean a third element can potentially open up design avenues not present in a doublet?...such as allowing certain types of eyepieces to be used...or....? It has been my understanding that the fewer pieces of glass the light must pass through, the better - generally speaking since each element introduces light loss. Introducing a third element with the requisite increase in production cost and weight would logically be done with the expectation of some specific benefit - I'm just at a loss for what that benefit may be. Slightly improved color correction, a flatter field, sharper view, or something?
I've read all of your reviews on various 20x80's and I've read some on other sites about the triplet models, but there does not seem to be any specific mention of the benefits. Nor can I recall a side by side comparison between a 20x80 doublet and a 20x80 triplet.
(*paging Mr. Busarow, you have a call on line one, Mr. Busarow...*)
Clear dark skies...
MikeG
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Michael Gilmer - Member of the Meteoritical Society & Collector of Falling Stars.
Galactic Stone & Ironworks - Specializing in exotic and rare meteorite falls.
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Jay_Bird
professor emeritus
Reged: 01/04/06
Posts: 690
Loc: Nevada 36N 115W
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Hi Mike,
There may be more variables in image qaulity that the triplet would help control than just chromatic aberration. From what I gather there are limits to correcting CA unless special glass is used, espeically at f/4 or f/5, but there could be other factor that are addressed by the third lens element, like a flatter field or control of other aberration across the field (?). Others here will certainly know more.
Old folding cameras often came offered with either a basic triplet lens or a higher end 4-element lens, the latter with faster maximum f/stop and better edge sharpness at wider (lower f/stop) apertures.
Jay
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'these things stand like stone - kindness in another's troubles, courage in your own' Gordon
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12783
Loc: Cumberland, R I , USA42N71.4W
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Quote:
It has been my understanding that the fewer pieces of glass the light must pass through, the better - generally speaking since each element introduces light loss.
Not a good basis for comparison to a doublet.
First look at potential light loss.
A well coated lens adds two reflective surfaces to the total path. Properly applied multicoatings can reduce that reflectance to 0.5% or 0.25% per lens surface. So at most the added lens reduces light throughput by 0.5% to 1%, certainly measurable in the lab with the proper claibrated equipment, but impossible to see visually.
Now look at any potential benefits.
Could be used to increase CA correction, reducing CA blur. Would improve point contrast.
Could potentially be used to reduce Spherical Aberration, probably a more significant benefit than CA reduction, since this may be a more problematic aberration in fast optics.
Give up 1/2% of total light to get those corrections? You bet.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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Rick
Carpal Tunnel
Reged: 04/12/05
Posts: 2626
Loc: Tokyo, Japan
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Quote:
However, there are other problems that can degrade the view more than a little color fringing. Spherical aberration makes it impossible to achieve a pinpoint star, astigmatism turns it into a cross and coma creates comets around the field edges. I would personally rather have a well-figured achromatic doublet than a poorly-figured triplet any day.
Good points Milt. That better objective lens figure is what we pay for in a premium binocular. Not to mention a more sophisticated eyepiece lens group that gives us those wide, sharp-to-the-edge flat fields we enjoy so much. CA is the least important of the astro binocular aberations, but the one that seems to get the most attention unfortunately.
That said, having now at least peeked through most of the top-of-the-line giant binoculars on the market from Fujinon, Miyauchi, Nikon (except for the 20x120), Takahashi, and Steiner, I'd have to say the only binocular that has ever truely blown me away has been the Kowa Highlander Prominar. The images it puts up are like Hi-Definition television.
clear skies,
Rick
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www.japanastro.com
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milt
sage
Reged: 09/13/04
Posts: 440
Loc: Arizona
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Quote:
the only binocular that has ever truely blown me away has been the Kowa Highlander Prominar
Hi Rick,
The Highlander Prominar has superbly corrected optics that were superior to Borg 100ED objectives in my tests. However, no binocular is perfect and the Highlander does exhibit field curvature and mild astigmatism near the field edges. It is just so good on-axis that I am willing to overlook those issues.
Best regards,
Milt
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Rick
Carpal Tunnel
Reged: 04/12/05
Posts: 2626
Loc: Tokyo, Japan
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Quote:
However, no binocular is perfect and the Highlander does exhibit field curvature and mild astigmatism near the field edges. It is just so good on-axis that I am willing to overlook those issues.
Is that with all 3 mags or just the 70deg AFOV 32x? I think I peeked through the 21x eyepieces with 65deg AFOV and don't recall seeing it.
The 72deg AFOV Nikon 18x70 Astroluxe I recently acquired also has field curvature. But it has better eyerelief and is lighter/easier to handle than the Fuji 16x70.
cheers,
Rick
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www.japanastro.com
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darylf96
Pooh-Bah
Reged: 08/28/04
Posts: 1246
Loc: Danville, California
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The Apogee RA-88-SA has triplet objectives that are termed "semi-apo". A triplet ojective is not necessarilly fully collor corrected.
Regards
Daryl
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Intes Micro MN66 - Meade 10" SCT
Skywatcher 150mm f8 Achro
CGE Mount - DiscMount DM-6 on Meade Field Tripod
with SkyCommander DSC
Lumicon 80mm Super Finder
ED80 w MoonLite focuser on CG5A-GT mount
WO ZenithStar ST 80mm/WO B-viewer
Astro-Tech AT80 Refractor f6.9 APO
On SV M1 mount & Grab-Go Tripod
Stellarvue 20x85 binos - Unimount
Kunming United Optics 7x50 binocs
Canon Rebel XT, Canon 20D, SB ST8XE
Orion DSCI, Meade DSI
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Michalis S
member
Reged: 06/07/05
Posts: 38
Loc: Greece, Athens
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So guys, here are the specs for those bino's:
Objective diameter: 80 mm
Magnification: 20x
Lens design: triplet objective lenses
True field of view: 56m / 1000m (3.2°)
Exit pupil diameter/distance: 4 mm / 17mm
Twilight factor: 40
Coating: Full broadband multi-coating
Prisms: BAK4 Prisms
Weight about 2400 grams
So I guess they will perform just fine.
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Orion Optics (UK) 10¨ Dob,labda/6, Hilux coatings
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milt
sage
Reged: 09/13/04
Posts: 440
Loc: Arizona
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Quote:
Is that [field curvature] with all 3 mags or just the 70deg AFOV 32x? I think I peeked through the 21x eyepieces with 65deg AFOV and don't recall seeing it.
Rick, I only have the 32x ep's. When I wrote my CN review I consulted with other Highlander owners and their younger eyes were better able to adapt to the field curvature than mine. Outside about 50% radius I would have to refocus to get stars as pinpoint as the center.
Another Highlander issue is eyepiece diameter. I have the old style with fold-down eyecups and find them very comfortable. When I tried Rich's new ones with twist-up eyecups I discovered that I had a, shall we say, "nose interference" problem.  Rich had no such problem and the eyepieces were otherwise fine.
This all goes to show that there are a myriad of factors that combine to provide a pleasing view. Optical quality, as my old prof used to say, is "necessary but not sufficient."
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Clear skies, Milt
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Chris Nicholl
super member
Reged: 01/05/04
Posts: 118
Loc: Exeter, NH
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Ed-
I've looked through the reviews, articles and cn reports section, and haven't been able to find anything by you on the Oberwerk 20x80 Deluxe II's. Can you (or someone else) point me in the right direction?
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Orion XT10
William Optics 66mm SD
Denkmeier Std - dual arm PowerSwitch
Oberwerk 20x80 Deluxe IIs on UA TMount Light
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12783
Loc: Cumberland, R I , USA42N71.4W
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Quote:
I've looked through the reviews, articles and cn reports section, and haven't been able to find anything by you on the Oberwerk 20x80 Deluxe II's. Can you (or someone else) point me in the right direction?
Other than focus style, you could refer to all the info on the Garrett 20x80 Gemini. Same model.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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