EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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Well, there aren't many binoculars in those sizes, so you might be already guessing at which I intend to compare. But don't go getting all anxious, you know how long it can take me to get through a series of tests comparing binoculars. A few months wouldn't be too short a time and may not be long enough.
For starters, I can give you some of the preliminaries I've measured.
Garrett Optical 22x85 Signature
full aperture appears to be 84mm
36mm or 43% center of aperture provides 100% illumination of exit pupil
when set to distance exit pupil = 3.94mm
magnification therefore is about 21.3x, call it 21x
21x84 with 43% of aperture providing 100% illumination
William Optic 22x70 Apochromat
full aperture appears to be 70mm, may be 71mm
35mm or 50% center of aperture provides 100% illumination of exit pupil
when set to distance exit pupil = 3.36mm
magnification therefore is about 21.1x or 20.8x, call it 21x
21x70 with 50% of aperture providing 100% illumination
Takahashi Astronomer 22x60
full aperture appears to be 60mm
50mm or 83% center of aperture provides 100% illumination of exit pupil
when set to distance exit pupil = 2.72mm
magnification therefore is about 22.05x call it 22x
22x60 with 83% of aperture providing 100% illumination
Well, the most outstanding measure of the above is the percent illumination of the Tak 22x60. I've now measured about 70 binoculars for illumination. Only 10 of them are over 40%. Only 4 of those reach 50%, two Fujinons, a Pentax and this WO 22x70. BUT only one exceeds 50%, the Tak Astronomer. And it shows that an astounding 83% of the center of aperture provides 100% illumination to the exit pupil. Now follow me here, I'll explain what this means.
Both the GO 22x85 and the WO 22x70 have 35/36mm of the center of the lens that is providing 100% illumination of the exit pupil. Then they both taper from 100% to zero at the edges. Assuming illumination in both is a constant slope of dropoff from full to zero at the edge, then the GO Signature will have slightly more total light delivered to the exit pupil, simply by nature of the wider aperture. But how much more? Surprisingly, not as much as you might think.
If you break down the light into concentric rings so you can calculate how much light from each ring, you can approximate how much light is delivered into the exit pupil. The central area of 35mm dia is full 100% lit. But, for example, take the 10mm wide ring between 45mm and 55mm diameter. 55sqrd minus 45sqrd leaves us with a ring of 3025-2025=1000sqmm. For sake of our example lets say that ring delivers 70% of its light. Therefore it effectively delivers about 1000sqmm x 70% = 700sqmm of light. This continues to decrease in each concentric ring further out until it drops to zero at the edges. You can do this for each concentric ring and approximate the total light in the exit pupil by adding up the subtotals for each individual ring. Two more things about this; you can simply take the entire area outside the central circle, and say that area provides 50% illumination; but the drop off slope is not constant.
The GO22x85 has almost 50% greater light gathering area than the WO22x70. But when you calculate total light, because the GO22x85 has a smaller percent of full illumination, the GO22x85 delivers only 37% more light than the WO22x70.
Now compare the WO22x70 to the Tak22x60. Well, the WO22x70 has 36% greater light gathering area more than the Tak22x60. But the Tak has so much of it's lens area that provides 100% illumination, 83% for the Tak vs 50% for the WO, that the Tak actually delivers the same total amount of light into the exit pupil as the WO22x70.
Now compare the GO22x85 to the Tak22x60. The GO22x85 has 2.0x the light gathering area as the Tak22x60. However, we have already determined the Tak22x60 delivers the same total amount of light into the exit pupil as the WO22x70. And we have already determined the GO22x85 delivers only 37% more light than the WO22x70. Therefore, the GO22x85 delivers only 37% more light into the exit pupil more than the Tak22x60.
The GO22x85 is very good at light delivery. At 40% full illumination, it ranks among the top 10 I've seen.
The WO22x70 has an even more efficient light delivery system. It measures at 50% full illumination, ranking it with 4 of the top 5 binoculars I've seen. I'd consider it excellent.
The Tak Astronomer 22x60 has such an efficient light delivery system that it is acting more like it is an excellent 22x70. It is so efficient that it is a superior 22x60.
edz
I want to thank Peter Staiger for loaning me two fine binoculars so I can make these and more comparisons over the next few months.
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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pcad
Carpal Tunnel
Reged: 01/17/05
Posts: 1767
Loc: Connecticut
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I was rooting for WO to make the very popular 66ED scopes into binoculars since they were demo'd a few years ago. I wasn't going to let the binoculars based on their larger ED scopes slip away. I was able to get them for the NEAF price last year.
I was fortunate to be able to get a used Tak 22x60 earlier this year. I figured that it would hold it's value and I'd be able to see for myself what they are like.
Despite using and enjoying these binoculars I knew I wouldn't do a comparison review justice. I just don't have the time, inclination or ablity to do such a review.
Fortunately Ed doesn't live too far from me and NEAF presented an ideal opportunity to loan them to him.
I have a few suspicions about why they are such different instruments. I'm as interested as anyone here as to what his conclusions will be. He's already found out more about these binos in one day than I have in 6 months.
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Peter
Telescopes 25 - 318 mm
Binoculars 15 - 88 mm
Microscope 50x - 1000x
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Mike Hosea
Post Laureate
Reged: 09/24/03
Posts: 3927
Loc: "Metrowest" Boston
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I had not heard of the WO22x70s before this. The pictures on the WO web site look to me like it's based the 22x85 in most respects but adapted to the different lens cells and premium objectives.
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Mike
Stuff that I use:
- 7" f/6.7 home-built Newt, eq platform, Pentax 40XW and 5XO, Tele Vue 13E and 2x Barlow, ZAO-II 6mm
- 120mm f/8.3 home-built grab-n-go Newt with 7-21mm Nikon Zoom
- Canon 15x50 IS and Eagle Optics 12x50 Ranger binoculars
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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The back end of the WO22x70 is identical to the back end of the GO22x85. Right up to the first smooth ring on the barrels, right in front of the prisms. In fact, if you cut the binocular right at those smooth rings it would be the Oberwerk Ultra 10x50.
The 70mm objective light cones deliver light better through that back end system.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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BobinKy
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EdZ...
For me, this will be a very interesting review, as I use the GO Signature 22x85. I agree with Peter, I have already learned more from your first post than I have on my own during the past 12 months.
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Bob
38°N
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pcad
Carpal Tunnel
Reged: 01/17/05
Posts: 1767
Loc: Connecticut
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I wouldn't say it's based on the 22x85 so much as it shares the body of the 7x50, 10x50, 10.5x70, 15x70, 15x85, 22x85, 20x110 and the 28x110 binoculars that Oberwerk call Ultras and similar ones sold by a number of others. I belive the front end is from the 70mm Zenithstar ED scope and uses FPL-51. As far as I can tell the eyepieces are those found on the 10x50, 15x70, 22x85 and the 28x110.
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Peter
Telescopes 25 - 318 mm
Binoculars 15 - 88 mm
Microscope 50x - 1000x
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BobinKy
Carpal Tunnel
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Posts: 1682
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EdZ...
Among other nitty gritties--I hope you compare the current price for each of these models.
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Bob
38°N
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BobinKy
Carpal Tunnel
Reged: 04/27/07
Posts: 1682
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Peter...
This is getting more interesting by the minute--I also use the WO ZenithStar 70mm ED scope.
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Bob
38°N
Edited by BobinKy (04/22/09 12:16 AM)
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EdZ
Professor EdZ
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Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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This first study should also highlight for our readers another important fact about binoculars. All to often discussions of exit pupil are brought up and inevitably it leads to thinking larger exit pupil is brighter. Well, that forces you to assume that all binoculars being compared are of the exact same quality and construction. It does not take into consideration the illumination of the exit pupil. It assumes the percent illumination is the same in every binocular. Well, we know that is not the case.
Look here at the WO22x70 and the Tak22x60. By the standard basic discussion of exit pupil, you would be lead to believe the WO22x70 will be brighter. But the far greater percent illumination of the Tak equalizes the light delivered into the exit pupil. So, here's a case where we have equal power binoculars, the WO22x70 has a 3.3mm exit pupil and the Tak22x60 has a 2.7mm exit pupil, and yet the amount of light delivered to the exit pupil is equal. It's all very much dependant on illumination.
You cannot assume just because a binocular has a larger exit pupil that it will deleiver a brighter image. That forces you to accept that there are never differences in the quality of the delivery system. Again, we know that quiite often is not the case. Trying to assess brightness without determining illumination can be quite misleading.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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Mike Hosea
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Reged: 09/24/03
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Loc: "Metrowest" Boston
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Quote:
and yet the amount of light delivered to the exit pupil is equal.
Even after accounting for the difference in AFoV?  It's a bit perilous to speak of the exit pupil as a whole. I take it you mean that the smaller aperture may deliver more light at a given apparent field angle, primarily because the corresponding light cones are less obstructed by limited-size prisms but also possibly due in some measure to transmission differences. If this happens "enough" (I believe you described a Riemann Sum approximation to a certain integral), then the smaller aperture may indeed deliver an overall brighter view.
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Mike
Stuff that I use:
- 7" f/6.7 home-built Newt, eq platform, Pentax 40XW and 5XO, Tele Vue 13E and 2x Barlow, ZAO-II 6mm
- 120mm f/8.3 home-built grab-n-go Newt with 7-21mm Nikon Zoom
- Canon 15x50 IS and Eagle Optics 12x50 Ranger binoculars
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daniel_h
sage
Reged: 03/08/08
Posts: 482
Loc: VIC, Australia
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and the WO is offering free intl shipping -i loved my WO 66 -don't think the wife will agree even though our government just gave us 900 as a recession breaker
Peter, if you have both which one are you keeping 
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regal 10x42, 10x50ultras, 15x70 ultras, 20x80
Oly e-500, vixen 100/1000 with 0.965"/1.25",
2 old sturdy tripods for the bins (slik & velbon)
zeiss f5.6 refractor/lens (under construction)
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Wes James
Post Laureate
Reged: 04/12/06
Posts: 3450
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Edz-
Wow.... a lot of info- and a lot of posts here. You've obviously been busy! I was really happy to hear that you were going to be reviewing these 3 bino's, as I have the W/O and Tak's both as well, and have recently kind of been interested in the Garrett's. Your technical knowledge and testing methods are unparalleled anywhere... so I look forward with great anticipation to your continued information on this great trio! What an opportunity to have all 3 together at one time.
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Wes
Atlantic Beach, FL
Some bino’s from Miyauchi 5x32 Binon's up through Garrett 20x110 Signature's,
Some telescopes from a Stellarvue 80mm NHNG up through a couple of 8” reflectors…
And a wonderful 4.25" Delmarva Shiefspiegler!
Some good friends, made here on C/N.
Oh- several cats and a wonderful wife!
Anyone want a cat???? :-O
"When your work speaks for itself- Don't Interrupt" -Gamble Rogers
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RichD
professor emeritus
Reged: 11/08/07
Posts: 563
Loc: Derbyshire, UK
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Very interesting results. I guessed the Tak's illumination would be highest but i never expected 83%! Takahashi must have taken great care in producing these.
Any observing reports with the WO and the taks edz?
I would love to see a similar review of the 18x70 nikon astrolux. I suspect these would show very high illumination too, owners often talk of brighter views than the fujinon 16x70, despite the smaller exit pupil.
Thanks again Edz
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Clear skies
Rich
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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Quote:
Quote:
and yet the amount of light delivered to the exit pupil is equal.
Even after accounting for the difference in AFoV? It's a bit perilous to speak of the exit pupil as a whole. I take it you mean that the smaller aperture may deliver more light at a given apparent field angle, primarily because the corresponding light cones are less obstructed by limited-size prisms but also possibly due in some measure to transmission differences. If this happens "enough" (I believe you described a Riemann Sum approximation to a certain integral), then the smaller aperture may indeed deliver an overall brighter view.
Perhaps I use the wrong words there. What I am measuring is illumination. How well does any small sample point on the aperture illuminate the exit pupil. So I should say the amount of illumination in the exit pupil. I'm making the inference above that any test point on the objective that delivers light to only 50% of the exit pupil is delivering only 50% the amount of light entering at the point, and so on. Of course, this is caused by internal vignette, where ever it occurs, probably mostly, if not all, in the prisms.
This measure of light delivered into the exit pupil is captured by moving a small laser over the surface. The test gives the result of a 2mm section of the binoc aperture. By moving the laser around, I test various positions of the binoc aperture. See the 22x85 thread where I show pictures of the procedure. Basically this is a 1-2mm aperture target laser tested over various positions on the surface of the full binocular aperture. It seems really to not be dependant on fov. For instance, I've tested seven different 20x80 all with the same method. Most of those 20x80s have nearly identical fov (all near 60-63 Afov), yet they produce illumination that ranges from <5% fully illuminated to 40%. Another example is three binoculars with Afov of 43-46°, yet they show illuminations of 25%, 50% and 83%.
Mike, I think your math skills are a bit beyond mine, but I think if I interpret correctly, I'd say yes I am essentially summing (integrating?) the result from a large number of samples taken over the surface.
Quote:
Here's a method I use for measuring effective aperture. It is also used to determine the percent of the objective that provides 100% illumination. It's really quite simple. You can refer to the post (EdZ 02/27/09 06:07 PM) in this thread to read the description of what can be measured or just follow further down to the picture presentation to see how its done.
Measuring Effective Aperture with a Collimating Laser Target.
edz
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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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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Quote:
Any observing reports with the WO and the taks edz?
as I mentioned in the first post, even the simple stuff, getting out to veiw side-by-side, will all take some time.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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Jim Rosenstock
Post Laureate
Reged: 07/14/05
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Loc: MD, south of the DC Nebula
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Quote:
EdZ...
Among other nitty gritties--I hope you compare the current price for each of these models.
A quick web search turned up a price of $822 for the WO 22X70s; apparently the Tak22X60s are no longer available new, but the last price they sold for new was approximately $1150....I saw one used pair listed for 800-something GBP. 
The Garrett Signature 22X85s cost $500.
After reading Edz's earlier posts on the Garretts, and especially his analysis of illumination issues, I bought a pair of the 22X85s....and immediately lost interest in using my "entry level" 25X100s and 22X100s....the premium Garretts are that much better.
Now, it seems that the WO and Tak 22's might well provide similar performance and illumination, in a smaller package.
Their prices, of course, are anything but smaller. Ahhh well, as always, you get what you pay for. IF you're lucky....
Cheers,
Jim
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RichD
professor emeritus
Reged: 11/08/07
Posts: 563
Loc: Derbyshire, UK
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Sorry, missed that (trying to read quickly at work)
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Clear skies
Rich
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Mike Hosea
Post Laureate
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The reason I was poking (half joking) is that the exit pupil is the superposition of an infinite number of exit pupils, each corresponding to a different point in the view. Every complete visual telescope system has an effective aperture geometry for any given point in the view. Hopefully, this is circular and matches the quoted objective diameters for points near enough to the center of the view (but you have often observed otherwise). Since the binoculars in question here all have this property, and probably they have similar transmission percentages, the 70mm binos should be brighter paraxially. That is to say, you should be able to see fainter stars dead center in the view. However, the area of the effective aperture gets reduced sufficiently far off-axis because something obstructs part of the light cone from the objective lens. As you say, it's almost always a prism, but eventually the field stop of the eyepiece will completely obstruct some light cones. It's the curse of being a mathematician to see these somewhat different physical things as different examples of the same abstraction. Anyway, because of their superior illumination profile, the Taks should see deeper sufficiently far away from the center of the field. However, pressing further afield, as soon as we run out of apparent field in the Taks, the 22x70s should see a lot deeper (because the Taks don't show anything at all behind the field stop).
For a single datum to compare, the total illumination is OK, but a lot of complexity can hide behind it. Ideally, you could compare illumination profiles in graphical form, e.g. something like the attached. [snip] You could compare just over the apparent field angles they have in common, or you could add it all up for both and compare. [snip] I just pulled this data out of the air. It is normalized to the 60mm aperture (y=1 is 100% illumination of 60mm). [snip]
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Mike
Stuff that I use:
- 7" f/6.7 home-built Newt, eq platform, Pentax 40XW and 5XO, Tele Vue 13E and 2x Barlow, ZAO-II 6mm
- 120mm f/8.3 home-built grab-n-go Newt with 7-21mm Nikon Zoom
- Canon 15x50 IS and Eagle Optics 12x50 Ranger binoculars
Edited by Mike Hosea (04/22/09 05:37 PM)
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Mike Hosea
Post Laureate
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Loc: "Metrowest" Boston
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Ah, good, I screwed something up and nobody called me on it yet. The total illumination isn't the area underneath one of those curves, it's the volume under the surface of revolution. It turns out for the profiles above, the smaller aperture has 8.9% more total light over 46 degrees of AFoV. Extending to 66 degrees, however, the larger aperture wins out with 17% more.
I guess the picture isn't that much help to estimate things at a glance after all.
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Mike
Stuff that I use:
- 7" f/6.7 home-built Newt, eq platform, Pentax 40XW and 5XO, Tele Vue 13E and 2x Barlow, ZAO-II 6mm
- 120mm f/8.3 home-built grab-n-go Newt with 7-21mm Nikon Zoom
- Canon 15x50 IS and Eagle Optics 12x50 Ranger binoculars
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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I was waiting for you to pick that up Mike. 
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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harbinjer
super member
Reged: 12/17/08
Posts: 126
Loc: Southeastern Minnesota
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Very interesting Mike. I too saw the idea of the Riemann sum, but alas forgot the name. My math teachers should be proud. Also very good intuition on EdZ's part.
So it is possible to figure out what the actual size of the "hat" is, and how much deeper you can see? Also I'm not sure how AFOV figures into this. If you can see are larger field, then you must be getting more light, right? Does that mean the in narrower FOV the field stop blocking that light, or is it just being scattered?
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Dirk Jan
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Reged: 04/18/09
Posts: 28
Loc: Rotterdam, Holland
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Quote:
I guess the picture isn't that much help to estimate things at a glance after all.
Ohw, in my opinion it certainly is. Visualizing it like that explained the issue at hand very much to me!
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"And through the drifts the snowy clifts
Did send a dismal sheen:
Nor light of moon nor stars we ken--
The clouds were all between."
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EdZ
Professor EdZ
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Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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There may be a difference in illumination across the fov and illumination across the exit pupil. Several years ago Anton Jopko wrote a paper as a follow-up to the method I proposed here for measuring aperture and illumination. There is a link in the Best OF Threads under measuring deficiencies. You can search the internet for it under Anton Jopko - Vignette. He speaks of a distinct diifference between the two, and what I believe I am measuring is illum across the exit pupil. I'm sampling with a 2mm dia light source on the objective, and the exit pupil is fixed by the power, regardless the fov, which is fixed by the diameter of the field stop. But I would encourage Mike and any others to read Anton's paper to help answer if I am correct in my thinking.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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Mike Hosea
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Quote:
So it is possible to figure out what the actual size of the "hat" is, and how much deeper you can see? Also I'm not sure how AFOV figures into this.
As Ed goes on to mention, there is a difference between illumination across the exit pupil and illumination across the view, if I understand what the former means. I probably won't have a chance to read the article that Ed points to, as I am sitting here at work and three things with a deadline of Monday just landed on my desk. I'll have to think more about what is being measured here and how useful it is. I guess my view is that brightness per unit area of the image projected on the retina is what really matters, provided there's not a lot of scattering from inferior optics, and provided the optics can actually deliver the light without too much aberration (a faint star is easily made invisible if not tightly focused). AFoV is not particularly relevant, since this (brightness per unit area) is a local rather than global thing. Brightness per unit area should be highest in the center of the view and lowest at the edge, generally. Most people (including myself) have difficulty seeing anything but a severe brightness gradient, but even if you can't see the brightness reduced near the edges, you may notice that the faintest things that show up in the center don't show up near the edge. The advantage of a better illumination profile is to show just as much, or nearly, away from the center as in the center. That's a nice feature for large objects and open clusters, cruising the Milky Way, etc.
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Mike
Stuff that I use:
- 7" f/6.7 home-built Newt, eq platform, Pentax 40XW and 5XO, Tele Vue 13E and 2x Barlow, ZAO-II 6mm
- 120mm f/8.3 home-built grab-n-go Newt with 7-21mm Nikon Zoom
- Canon 15x50 IS and Eagle Optics 12x50 Ranger binoculars
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daniel_h
sage
Reged: 03/08/08
Posts: 482
Loc: VIC, Australia
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obviously the Tak is the pick of the bunch (but the chances of getting one are buckleys) - which would people have out of the other two?
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regal 10x42, 10x50ultras, 15x70 ultras, 20x80
Oly e-500, vixen 100/1000 with 0.965"/1.25",
2 old sturdy tripods for the bins (slik & velbon)
zeiss f5.6 refractor/lens (under construction)
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BobinKy
Carpal Tunnel
Reged: 04/27/07
Posts: 1682
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Quote:
. . . but the chances of getting one are buckleys. . .
...daniel_h
I had to look this up in the phrase finder:To "have Buckley's chance" or to "have two chances, Buckley's or none". I was told it referred to an escaped convict called Buckley who survived in the outback for 30 years after being rescued by Aboriginals. It was considered impossible for convicts in Australia to survive in the outback - hence the saying. Daniel must be referring to the possibility of acquiring the TAK--and not to EdZ's chance of completing his Magnum Opus of Illumination by Friday noon--and since I already have the GO--I opt for the WO.
. . .
Some guys have nothing but good fortune. Think what strong biceps EdZ will develop after bench pressing (er, field testing) the triple glass--GO/WO/TAK. 
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Bob
38°N
Edited by BobinKy (04/22/09 08:19 PM)
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pcad
Carpal Tunnel
Reged: 01/17/05
Posts: 1767
Loc: Connecticut
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Hi Daniel,
As for which I would keep, I would hold on to the Tak. I have several places I might use the WO and will probably keep it also.
These days, with the Tak discontinued, more people seem to want them. When they were available new, you would think they'd be rather popular. I don't recall that being the case. It was always a very expensive instrument with limited aperture. Despite what Ed has found, it's still only 60mm. I remember people comparing its FOV to looking through a straw.
Its FOV is listed as only 2.1 degrees, while the WO has a 3 degree FOV. The magnification is the same and the AFOV for the WO is 66 degrees. That means the AFOV of the Tak eyepieces is about 46 degrees. That isn't a real expansive view for most binoculars. While narrow, it might help explain why it's such a crisp view across the FOV.
So while it's an excellent specialty binocular the Tak may not be what many want in a binocular.
I'm waiting to hear what Ed has to say about this kind of stuff. He'll have tested them while I'm only guessing.
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Peter
Telescopes 25 - 318 mm
Binoculars 15 - 88 mm
Microscope 50x - 1000x
Edited by pcad (04/22/09 08:22 PM)
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daniel_h
sage
Reged: 03/08/08
Posts: 482
Loc: VIC, Australia
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Bob, sorry about the buckleys slang - your story is perfectly correct though. that fov is very narrow - maybe too so, the WO might be the way to go, think its a little lighter than the GO...hmmm free shipping to Australia as well
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regal 10x42, 10x50ultras, 15x70 ultras, 20x80
Oly e-500, vixen 100/1000 with 0.965"/1.25",
2 old sturdy tripods for the bins (slik & velbon)
zeiss f5.6 refractor/lens (under construction)
Edited by daniel_h (04/23/09 01:30 AM)
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milt
professor emeritus
Reged: 09/13/04
Posts: 551
Loc: Arizona
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Quote:
The advantage of a better illumination profile is to show just as much, or nearly, away from the center as in the center. That's a nice feature for large objects and open clusters, cruising the Milky Way, etc.
Hi Mike,
Glad you jumped into this when you did because I didn't have time and not much now either. Ed has done some nice work measuring illumination, but if it was done with on-axis rays at various points on the objective, then he is measuring illumination at the center of the field. To measure off-axis illumination the laser must be tilted at a precise angle and then moved around the objective. I did this several years ago but it is a difficult setup because the angles are only a couple of degrees for a 5° field.
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Clear skies, Milt
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Mike Hosea
Post Laureate
Reged: 09/24/03
Posts: 3927
Loc: "Metrowest" Boston
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Oh, so it gets clearer now. I maybe should say "never mind" at this point. If using a laser parallel to the axis, then I presume the drop in transmission is due to the drop in reflectance of the prisms at oblique angles. In that case, Ed has it exactly right, and everything I said was on a different, albeit related topic. The larger exit pupil for on-axis illumination would not necessarily be a brighter one if the light coming from the edges of the objective is cut down by a large percentage because the prisms are inefficient at the angle of incidence. I guess I'm too used to telescopes which aren't relying on prisms with such a fast light cone. Possibly the Taks are performing better in that measure simply because they have slower objectives?
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Mike
Stuff that I use:
- 7" f/6.7 home-built Newt, eq platform, Pentax 40XW and 5XO, Tele Vue 13E and 2x Barlow, ZAO-II 6mm
- 120mm f/8.3 home-built grab-n-go Newt with 7-21mm Nikon Zoom
- Canon 15x50 IS and Eagle Optics 12x50 Ranger binoculars
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KennyJ
Reged: 04/27/03
Posts: 12885
Loc: Lancashire UK
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< The larger exit pupil for on-axis illumination would not necessarily be a brighter one if the light coming from the edges of the objective is cut down by a large percentage because the prisms are inefficient at the angle of incidence. >
That sums up acurately my understanding of what EdZ's experiments have been indicating all along .
Kenny
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If everyone is thinking the same thing , no-one is thinking - General George S.Patton
Zeiss 7 x 42 BGAT
Captain's Helmsman 7 x 50
Nikon 10 x 42 Superior E
Swift Audubon Kestrel 10 x 50
Helios 15 x 70 Observation
Strathspey 20 x 90
Televue 76 APO
Zeiss 85 Diascope
Helios 102 f5 refractor
Various eyepieces barlows tripods mounts etc.
Panasonic Lumix DMC - TZ5 digital camera
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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Quote:
measuring illumination, but if it was done with on-axis rays at various points on the objective, then he is measuring illumination at the center of the field.
Quote:
The larger exit pupil for on-axis illumination would not necessarily be a brighter one if the light coming from the edges of the objective is cut down by a large percentage because the prisms are inefficient at the angle of incidence.
I'd say yes to both of these statements.
Measuring Illumination by sampling various points on the objective gives a profile of how the entire objective contributes to the total illumination. It's interesting to watch as the target laser is moved around the face of the objective that the crosshairs in the target laser projected image never move from the dead center spot in the projected image (a clear indication the the targetr is indeed on-axis, even when it is say 30-40mm off centerline). However the complete shape of the projected exit pupil does change. And this gives the clue to precent illumination from that point on the objective, allowing the mapping to take place. So, while the illuminated point is in the center of the field, the source light is moved around the entire objective, therefore allowing the observation of what contribution is made to that central image of that point from this particular position on the objective.
For any given stellar point in an image, even a star dead center, as Mike alluded to earlier, the image is made up from an infinite number of rays. The laser shows this, for instance, when the laser is 30mm off centerline it still projects a point of crosshairs dead center in the projected image. It is this precept that provides for the basic understanding of larger aperture = greater resolution.
Of course, if an on-axis ray produces a smaller than 100% illumination from some point on the objective, I'd say it is reasonable to assume an off-axis ray will not increase the illumination at that point on the objective.
Rays from the entire diameter of the lens make up every point in the image. If a star at the center of the view did not receive rays from the edges of the objective, but only from the center of the objective then that star would have an Airy disk size determined only by the portion of the objective from which it did receive rays. In order for the Airy disk size of a star to be congruent with the objective diameter, the point in the image MUST receive rays from every point on the objective. The question here is, how much light is in those rays.
This attempts to show what happens to the total light in the exit pupil when rays further of centerline begin to lose some of the total light from entering ray to exiting ray. This cannot be seen when testing entire exit pupil from entire lit objective. It can only be seen when testing with light on the objective at small isolated sampling areas, ie., the 2mm laser target projected thru the objective.
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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EdZ
Professor EdZ
Reged: 02/15/02
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Loc: Cumberland, R I , USA42N71.4W
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Field Sharpness of the three binos
tested on Theta Serpens mags 4.5-5.0 @ 22". In these binocular that gives me about 460-480 arcseconds apparent. My typical measure for what I rate as usable fov would be 600 arcsec apparent, so this is a more stringent test than total usable fov. But this 22" star was available and it gives me the opportunity to compare the three. I previously measured the GO22x85 and it deteriorates to worse than 600 arcseconds by 70% out from center. Based on what I saw in the Tak, it would do better than 600 at the very edge.
Garrett Optical 22x85 Signature
full aperture is 84mm and magnification is 21.3x
Full Tfov is 3.04°, therefore Afov is 65°
Limit of 22" sharpness is ~60% out from center
Sharp Fov to 468 arcsec apparent is 1.8°
William Optic 22x70 Apochromat
full aperture is 70mm and magnification is 20.8x
Full Tfov is 3.0°, therefore Afov is 62°
Limit of 22" sharpness is ~60% out from center
Sharp Fov to 457 arcsec apparent is 1.8°
Takahashi Astronomer 22x60
full aperture is 60mm and magnification is 22.0x
Full Tfov is 2.2°, therefore Afov is 48°
Limit of 22" sharpness is 90% out from center
Sharp Fov to 484 arcsec apparent is 1.95°
As is often the case, the binocular with the widest Afov eyepieces seems to suffer from the least sharp fov. I've rarely seen binoculars vary from this, the exception being some of the most expensive and highest quality.
Here we have the GO22x85 with a very slight wider Afov than the WO22x70. Both have essentially a 3° Tfov. They are nearly equal in outer field sharpness. FWIW, in these tests, the WO came up just a few percent wider in sharp fov, not reported above.
I did measure a slight difference in the Tfov. Of course if my measured Tfov of each one is off by 2%, one higher and one lower, or if my measure of magnification is off by 2%, it would account for the difference in Afov. There are some apparent differences on the outside of the eyepieces, however this may simply be a difference in outer housing on the GO to accept filters. A laser pointer seems to show the lenses appear to be the same configuration.
Then we have the Tak22x60. Now the total fov is only 2.2° and the Afov of the eyepieces is only 48°. BUT, look what we get out of that. The outer field sharpness of the same star extends out to 90% of the Tfov and that gives us a 1.95° sharp Tfov. The narrow TaK, less that 75% of the total FOV of both the others, actually has a wider sharp fov than both of them. The Tak has approx 10% wider sharp fov than both these other binoculars.
In all three of these binoculars I could see M26 and NGC6712 at the same time. In both the WO and GO, these two objects span across about 75% of the Tfov. Actually in the Tak I had to pan slightly to get each just into the edge of the fov, because they are ~5% wider apart than the Tak Tfov. But in the Tak, I could see both of those in the outer few % of the fov. Both M26 and NGC6712 are about visual mag 8. M26 has a brightest star of mag 10.3 and NGC6712 has a surface brightness approx mag 12.
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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EdZ
Professor EdZ
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Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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Eye Relief
Garrett Optical 22x85 Signature
17 total minus 8 recess = 9 usable
William Optic 22x70 Apochromat
17 total minus 8 recess = 9 usable
Takahashi Astronomer 22x60
14-15 total minus 2 recess = 12 usable
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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KennyJ
Reged: 04/27/03
Posts: 12885
Loc: Lancashire UK
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Those eye relief figures present another distinct advantage of having binoculars that accept standard eyepieces !
Kenny
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If everyone is thinking the same thing , no-one is thinking - General George S.Patton
Zeiss 7 x 42 BGAT
Captain's Helmsman 7 x 50
Nikon 10 x 42 Superior E
Swift Audubon Kestrel 10 x 50
Helios 15 x 70 Observation
Strathspey 20 x 90
Televue 76 APO
Zeiss 85 Diascope
Helios 102 f5 refractor
Various eyepieces barlows tripods mounts etc.
Panasonic Lumix DMC - TZ5 digital camera
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BarrySimon615
Pooh-Bah
Reged: 03/01/04
Posts: 1279
Loc: New Orleans, LA
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Ed et al -
I have just spent the last half hour reading thru the thread and I once again have to applaud your diligence.
Over the years I have gone thru my fair share of binoculars, rejecting some when I found better, constantly upgrading the collection. One brand/style that I have had somewhat of a love-hate relationship with has been the Pentax PCF series in it's various forms starting with the PCF III. I love the ergonomics and the sharpness of the view toward the field edge, but I hated the narrow fields. At this point, I only have one pair left (that I intend to hold on to) - my Pentax PCF 16x60's with a 2.8 degree field, narrow, but good virtually to the edge. Pentax also had and may still have available the Pentax PCF 20x60's which I have referred to as a "poor man's" Takahashi 22x60. If you have any testing information on those, it may be interesting to change your 3 way comparison to a 4 way comparison.
Barry Simon
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EdZ
Professor EdZ
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I did do a minireview on the 20x60. There is data here (and in my notebooks) somewhere.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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EdZ
Professor EdZ
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The issue raised by Mike H here needs to be re-addressed. It has been raised before and again recently by Milt and Tony.
The laser I am using projects a target with cross hairs. There is a link testing with a laser and other methods to a discussion showing the setup.
The target cross hairs center point is used to measure extent of aperture. No problems there, as that center of the crosshairs point in the projected image is always straight on. However this laser projects a target in which the circle seen in the photos measures 5° across (5" dia at a distance of 56 inches). When I use the laser on top of the binocular, only the center of the crosshairs is a perfect on-axis point. All the rest of the image is actually off-axis.
The measurements that I give for extent of aperture use the center of the cross hairs. By definition, it measures the edges of the aperture and if it can still be seen, as Milt says, then 100% of the aperture is used to illuminate that single on-axis point. All the rest id off-axis. So the statement 83% illuminated to 100% should mean the image is 100% illuminated from off-axis light that enters at 83% out on the aperture. The position is 83% out from center. The full circle of the laser that shows in the dead center still shows at 83% out from center.
Sorry for any gross confusion I may have caused. I hope this clarification agrees with what everyone else interprets.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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milt
professor emeritus
Reged: 09/13/04
Posts: 551
Loc: Arizona
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Quote:
the statement 83% illuminated to 100% should mean the image is 100% illuminated from off-axis light that enters at 83% out on the aperture
Hi Ed,
Good clarification with one niggling question: Isn't any ray that is parallel to the optical axis considered an on-axis ray regardless of where it enters the objective? My understanding is that rays that enter away from the center are called peripheral rays, which could be on-axis (parallel to the optical axis) or off-axis (at an angle to the optical axis). Tony can beat me up if I have this wrong. 
For those reading (if anyone still is) who are still unclear on what we are talking about, for our brain to "see" a star at the center of the field there must be a bundle of parallel rays coming straight out of the exit pupil. It doesn't matter how big the exit pupil is or even if it is round; as long as the rays are parallel and coming straight out, we will see a star at the center of the field. Of course the smaller the bundle the dimmer the star, which is what Ed has been measuring.
If the bundle of rays coming out the exit pupil are parallel but leave at an angle we will still see a star, but moved away from the center of the field. Enough, already!!!
Thanks for your patience,
Milt
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BobinKy
Carpal Tunnel
Reged: 04/27/07
Posts: 1682
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Thanks EdZ.
Thanks Milt.
Yup, there are still some of us lurking about.
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Bob
38°N
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Mike Hosea
Post Laureate
Reged: 09/24/03
Posts: 3927
Loc: "Metrowest" Boston
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Quote:
The full circle of the laser that shows in the dead center still shows at 83% out from center.
Bear with me here, because I'm a little slow on the uptake. By watching the center point of the projected beam we can measure the extent of the aperture forming the on-axis point in the view, and although the projected hologram may be useful for reducing the measurement error, it isn't technically relevant to this determination.
However, the projected hologram is expanding at a known rate, so we can use it to explore off-axis illumination in the same way, i.e. by performing he same exercise except tracking not the center point but a point in the projected horizontal hologram cross-hair a fixed distance from the center point. Doing this for the full range of angles, from zero to half the TFoV, would produce data that could be plotted like my previous graph.
Why would you ever be interested in the full circle being visible or not? The portion of the aperture that is shared in common to illuminate all points along a circle in the view corresponding to a certain field angle does not determine the brightness of that circle because each point on the circle is illuminated by some part of the objective outside that area used in common.
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Mike
Stuff that I use:
- 7" f/6.7 home-built Newt, eq platform, Pentax 40XW and 5XO, Tele Vue 13E and 2x Barlow, ZAO-II 6mm
- 120mm f/8.3 home-built grab-n-go Newt with 7-21mm Nikon Zoom
- Canon 15x50 IS and Eagle Optics 12x50 Ranger binoculars
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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WEll, it's not so much that I'm intersted in the circle. Your first two paragragps are exactly correct and that's what I do. But it just so happens in the Fujinon 10x50 it (the circle) can be seen and I happen to know it is 5.1° wide. I can't even see the circle in the 22x85. But as you suggest, I can at least see the cross hairs (out to some length of the cross hairs) just inside that circle. In fact, this is what I measure when I'm conducting the illumination test, the length of the cross hairs (and the reduction in length), as I've shown in the previous picture display.
To answer Milt, the only single point that the laser is projecting that actually is on-axis is the center dot of the cross hairs, regardless of where I position the laser on the objective. And, to reinforce what you said, yes, in fact the center of the cross hairs will always be on-axis regardless of where I position the laser on the objective.
But the most important part here is that the laser actually projects a cone of light with only "one single ray" parallel, the center dot. This is where I misintrepreted all along. All the remaining rays coming out of the laser are at a progressively greater angle. For example, the length of the cross hairs inside the circle may be made up of 50 dots, or 50 rays. Each of those rays is at a progressively greater angle off axis, until we reach the circle, and those rays are tilted 2.5° off axis each side of the center to form that circle. So even when the laser is sitting on top of the objective dead center, only one ray is on axis, the center dot of the cross hairs. All the others are angled, and therefore off-axis.
This example is chosen only becasue the image is easy to visualize, but it's the same for any binocular: When the laser is sitting dead center on the Fujinon, the circle can be seen and we know at least that the laser is projecting a 5° wide cone of light thru that point of the objective. Hundreds of those little rays that make up the laser image are off-axis. Only one is on-axis. Same is true for wherever I move the laser over the objective.
If I were so industrious, I could actually count the dots along the cross hairs in the full projected image and determine at what angle each is being projected (for ex., 40 dots out, out of 50 dots on this side, = 2° as a proportion between 0 and 2.5°). That detailed count the dots data could be used to state something like "at 70% out on the objective, off-axis targets beyond 2° are not illuminated", and I would assume also that Mike could use this if he desired to create plots.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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Mike Hosea
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The method is a good one. So, just to verify one more thing, the percentage figure you quote that comes out of it is the percentage of the TFoV (just to be clear, along a diameter or by area?) that is fully-illuminated. In the 22x85 thread you noted that the measurement for the Fujinons was 40%, meaning that for the central 40% of the view (linearly or by area, according to your previous response), the entire objective is contributing light to the view. Beyond that the exit pupils have a shape that is the more or less like the intersection of two circular disks.
OK, so that might lead to one binocular appearing brighter than another simply because it has higher illumination over more of the off-axis field of view. As previously mentioned, another factor would be prism efficiency, which should be lower for parallel rays entering the edges of the objective. You'd need a single-beam laser and a photometer to explore that. I really don't know how much variation to expect, but the slower the objectives, the less of a factor it should be.
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Mike
Stuff that I use:
- 7" f/6.7 home-built Newt, eq platform, Pentax 40XW and 5XO, Tele Vue 13E and 2x Barlow, ZAO-II 6mm
- 120mm f/8.3 home-built grab-n-go Newt with 7-21mm Nikon Zoom
- Canon 15x50 IS and Eagle Optics 12x50 Ranger binoculars
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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Quote:
(just to be clear, along a diameter or by area?) that is fully-illuminated. In the 22x85 thread you noted that the measurement for the Fujinons was 40%, meaning that for the central 40% of the view (linearly or by area, according to your previous response),
linearly Mike,
I measure from center to edge of lens and report % out from center. So when I say 40% of the central area, the measurement I got was 40% out along a radius line of the aperture. It can then be used to refer to the central 40% of the diameter of the lens.
Then it would be stated, the central 40% diameter of the lens is illuminated by 100% of the fov. That's a little different than saying I'm getting 40% out in the fov.
I know area makes it much different, but I'm mapping location on the lens and essentially using that to picture what percent of lens diameter.
Where we really see this illumination or brightness come into play is when comparing some binoculars that have readings of only 10% to others with 40%-50%. 37 out of 69 binoculars show 100% fov illumination over ONLY 20% or less of the lens .
18 (more than 25% of all 69) of those were less than 10%. For the most part, although there are a few unpleasant surprises, the <10% list reads like a who's who of cheap binoculars, a few of which have been given glowing reviews by some users. Half of those are also binoculars that suffer from about 15% (7mm-9mm) reduction in true aperture.
Cross threading points, see the ratings thread
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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Mike Hosea
Post Laureate
Reged: 09/24/03
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Loc: "Metrowest" Boston
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Quote:
I know area makes it much different, but I'm mapping location on the lens and essentially using that to picture what percent of lens diameter.
It's fine. I was just trying to clarify which one it was. I think linearly is the best way of reporting it, too.
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Mike
Stuff that I use:
- 7" f/6.7 home-built Newt, eq platform, Pentax 40XW and 5XO, Tele Vue 13E and 2x Barlow, ZAO-II 6mm
- 120mm f/8.3 home-built grab-n-go Newt with 7-21mm Nikon Zoom
- Canon 15x50 IS and Eagle Optics 12x50 Ranger binoculars
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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There is an ongoing discussion that has unfortunately become somewhat disjointed across several different threads. It is all related to illumination, but appears in different places. I thought I'd put up this post with links to all the current discussions, of which a portion resides in this thread and the first two threads linked below. Also included are some of the past posts that have data related to the topic. While this topic is new discussion for some in these current threads, We've been having these discussions spread out for over 5 years.
Rating Binoculars
A portion of the discussion ctitiquing this method can be forund in this thread
EdZ's 22 x 85 GO Signatures
this thread has a written explanation of the procedure. It also has a pictoral essay showing the procedure.
Here is an older thread where I show the results of this test for the Small Binocular Series
Small Binoculars - Illumination of the Exit Pupil
Exit Pupil Profile of OberwerK Ultra 15x70
An earlier attempt at showing a plot of how the light is spread out in the exit pupil
Vignette in Binoculars!! Test Procedure
description of this same test - posted 4-5-04
Graphic of Off Center Exit Pupil
not only can this test be used to develop an illumination profile, but it very clearly allows one to see when light rays reaching the exit pupil are dramatically tilted, forming an off-center illumination profile.
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Glassthrower
Vendor - Galactic Stone & Ironworks
Reged: 04/07/05
Posts: 16348
Loc: Kuiper Belt
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This thread has been very illuminating (pun intended) and I have learned much about exit pupil. If I wasn't in the middle of moving right now, I'd sit down and completely digest this thread. For now, I'll flag it for later reading. I did manage to get through the first 1.5 pages though. 
The GO 22x85 is a fine binocular and I regret selling mine. But now, I am keen to acquire a Tak 22x60 - I always wanted one anyway, but now I can possibly afford one.
Thanks for this educational lesson EdZ and MikeH!
Best regards and clear skies,
MikeG
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Michael Gilmer - Member of the Meteoritical Society & Collector of Falling Stars.
Meteorites, Moon Rocks, Mars Rocks, Tektites, Fossils, Minerals, Crystals, & Trinitite.
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EdZ
Professor EdZ
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Went out this weekend for a little viewing for the first time in 6 weeks. Just a few comparisons in this group again.
checked the focal length of these three.
the GO22x85 is listed as f/4.7 and I come very close (10-15mm) to that by measure. So let's stick with that. f/4.7 makes it F=400mm.
The WO22x70 is about 10-15mm longer than the GO. So the WO22x70 is aprox F415mm and therefore is almost f/6
The Tak 22x60 is approx F=370mm, therefore is about f/6.2.
On the moon,
none show on-axis color.
the GO22x85 shows a band of lateral color, predominantly yellow towards the inside and purple towards the outside edge of the lens. It's a fairly thick yellow band, but not obtrusive. The GO is by far the fastest of these three binoculars and even if all else were equal (which its not), should show the most color just by nature of the faster f.
the WO22x70Apo shows a very thin band of lateral color. It can be almost not noticable. But keep in mind, the WO22x70 is f/6 and the GO22x85 is f/4.7. The GO and WO objective lenses have what I would call an identical signature when using a green laser pointer to shine thru the objective lens. Both are two element air spaced doublets.
the Tak22x60 shows no lateral color at all. I could not force any color. Well, not only is the Tak Astronomer a true Flourite objective, but also it is about f/6.2 the slowest of these three binoculars.
focusing on a pair of stars, gamma Delphinus, 9.6".
the WO22x70 does very well, gives a nice tight point for each star, has very minor spiking of the brighter star in the pair.
the GO22x85 shows the largest points when focused best. Stars don't get as small as seen in the WO22x70. On a close uneven pair it makes it just a bit more difficult to see the pair cleanly separated.
the Tak22x60 focuses to extremely fine pinpoint dots, half the size of the dots in the GO22x85. There are no minor spiking points coming off of even the brightest star. The pair is very well separated, the clean black space between the pair seemingly a bit wider that that seen in the GO22x85.
on Vega
the GO22x85 shows it as a white star with an obvious blue halo.
the WO22x70 shows a cleaner white star, little halo.
the Tak 22x60 shows pure white and the smallest point of the three. Even on a star as bright as Vega, it focuses a smaller dot and shows almost no points or halo around the clean dot.
The WO22x70 refines the image to somewhat better than is shown in the GO22x85. The focused dot is a bit smaller and the tiny spikes that eminate from the brightest stars are just a bit smaller. I'm not sure what I attribute this to, but it certainly doesn't hurt that it is f/6.
Although there is no question that the Tak is putting up the finest dot point image of these three binos, the GO22x85 seems to put up the brightest image. On targets such as M27, M71, M57, M15 and M11, it was the GO22x85 that to me seemed always to give the brightest image of the diffuse object and its surrounds. Shouldn't be too surprising as the GO22x85 does have far greater aperture. Even though the Tak22x60 has far better illumination than both these others, the much larger aperture seems to make up for that lost illumination.
So, for Apo images and finest pinpoints try the Tak. For deep sky, but a bit less refined image, try the GO Signature. Fairly obvious, but the WO22x70 falls in between. The WO22x70 shows better pinpoints than the GO22x85 but not as good as the Tak, and the image quality of the WO, although better than the GO, is not the same as the Apo correction of the Tak. In fact, although the WO22x70 is better color corrected than the GO22x85, it still shows false color and I'm not sure the WO22x70 should be called an Apo by any standard. ED perhaps yes, but Apo, I think not.
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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Gordon Rayner
scholastic sledgehammer
Reged: 03/24/07
Posts: 965
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Ed says: "Even though the Tak 22 x 60 has far better illumination than both these others...". By this , do you mean illumination of the image of a target at a certain angular distance off-axis? Or, do you mean illumination of a target at which the binocular is directly pointed?
"..the much larger aperture seems to make up for that lost illumination." ?? In what way? What do you mean? You seem to be saying that the 60mm. Tak illuminates better, then you say that the larger(70mm) "makes up" (equals or exceeds ?) the illumination of the Tak.
Your target is diffuse, so it is not a reduction in the size of the Airy disc, which comes from an aperture increase.
I have no personal experience with any of these three, except that the Tak body is obviously a Katsuma 7 x 50 (Tasco, Swift, Tasco USMC 7 x 50, etc. ) with the Katsuma glue reinforced(?) prism mounting method of mounting the near-copies of the B&L Mk. 28 prisms, the near-copy of the eyepieces and objectives, etc. I have been into enough of those Katsuma, with cracked gray glue, to not relish any further specimens, though I suppose that they may be better than some of the other things that are now around. The images are good, even if the internal mechanics are not the most durable. But perhaps durable enough for astronomy.
I have read this entire thread. It would be nice to have access to ZEMAX, or even the free version of OSLO, get some graphics into the exposition/discussion/controversy(?). A YouTube with some graphics? When so much depends upon choice of terminology ,there is opportunity for misunderstanding, if not fallacy, to creep in.
In 3074850 4/29/09, above, Mike Hosea said "Another factor would be prism efficiency, which should be lower for parallel rays entering the edge of the objective." ??
Why? For rays parallel to the optical axis ,let us assume that there is no clipping, and that total internal reflection in the prism takes place for targets at the center and edge of the field. If not Ed probably would have rejected them out of hand, and not bothered to evaluate.
Edited by Gordon Rayner (07/05/09 07:40 PM)
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Gordon Rayner
scholastic sledgehammer
Reged: 03/24/07
Posts: 965
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Milt: I like your posts on this topic. Very clear and unambiguous.
It is possible, especially with a quick reading , to get the impression, from the early to mid part of this thread, that , other factors being equal, a smaller aperture can increase the illumination(integrated energy, in an image spot of any size), in the focal plane, of the image of an axial and/or extra-axial point source target, which is impossible .
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BobinKy
Carpal Tunnel
Reged: 04/27/07
Posts: 1682
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EdZ...
I am glad you are still in the game of comparing these large (giant?) aperture binoculars. Thank you for posting your research. These are not lightweight binoculars, nor are the mounts that must accompany them.
. . .
Binoculars or scopes--one of my favorite summer night views is the open star cluster M7 (Scorpius) through Garrett Signature 22x85 binoculars. The cluster fits perfectly in the 3° FOV, with just the right amount of dark sky for framing. The bright 3.9mm exit pupil coming through two eyes just fills my mind with wonder and my imagination runs wild. Whenever, I have a problem to ponder, M7 through Signature 22x85 delivers the solution.
Somehow, none of the other optics I have access to deliver on this one object like the Signature 22x85. . . not the Fujinon 16x70 (wrong size FOV, not enough magnification). . . not the 70mm refractor telescope (a 20mm eyepiece comes close, 22x, but not enough light, 3.3mm exit pupil for one eye does not compare to Sig's 3.9mm exit pupil delivered simultaneously to each eye). . . not the 15-inch dob (a 30mm eyepiece again comes close with lots of light, 6.0mm exit pupil, but 64x is too much magnification for M7 in a 1° FOV, there is no aesthetic dark sky framing the cluster to invite imaginative wanderings).
Nothing I have delivers on M7 like the Garrett Signature 22x85.
So there you have it.
. . .
EdZ, in another thread , you gave us a formula for converting binoculars to telescope aperture mm equivalent. I pasted the formula in my binoculars spreadsheet. The Signatures 22x85 are equivalent to a 101mm (4-inch) telescope. That is something of value.
Thank you for giving us so much. You are the greatest! 
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Bob
38°N
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gmazza
super member
Reged: 03/10/09
Posts: 102
Loc: RS, Brazil, 29S 51W
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Didn't remember how many times I read this topic. Although a comparison between 22X binoculars. The final choice by me was the 15X85, some things posted here helped in this choice. The illumination of exit pupil, I wanted a good size and still a large illuminated exit pupil. The 15X model was not tested here but with the same prism housing I assume a very good pupil illumination profile too, at least the views are a big pleasure.
I am aware of the compromises of 15X magnification in astronomy, but, diffuse objects are great on this one, daytime observation too, as Zach pointed me on this, and I wanted to "Keep the doors open" for a high magnification binocular in future, some like the 30X80 in the recent dream binocular thread.
Clear Skies for you all
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Oberwerk Ultra 10X50
Garrett Signature 15X85
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gmazza
super member
Reged: 03/10/09
Posts: 102
Loc: RS, Brazil, 29S 51W
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Quote:
Although there is no question that the Tak is putting up the finest dot point image of these three binos, the GO22x85 seems to put up the brightest image. On targets such as M27, M71, M57, M15 and M11, it was the GO22x85 that to me seemed always to give the brightest image of the diffuse object and its surrounds. Shouldn't be too surprising as the GO22x85 does have far greater aperture. Even though the Tak22x60 has far better illumination than both these others, the much larger aperture seems to make up for that lost illumination.
Have you tried to mask the 85 mm and 70 mm to 60 mm and compare with TAK ? The 22X60 has state of art quadriplet lens with fluorite, the WO has FPL-51 ED, the Garret I do not find glass specifications. Would be interesting to compare them masked, at this time I found the very clear advantage of TAK 22X60 is the half weight comparing with other two, and the main compromisse is the narrow field of view.
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Oberwerk Ultra 10X50
Garrett Signature 15X85
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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no not yet.
edz
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milt
professor emeritus
Reged: 09/13/04
Posts: 551
Loc: Arizona
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Quote:
[From previous post by pcad] When inspecting the Tak 22x60 with a GLP, there was no evidence of it being anything other than a Fluorite doublet objective.
Hi Peter,
I am curious to know exactly what you saw with the GLP. True CaF2 does not scatter light so you will not see a green laser as it passes through, but you will see coatings. If it is an oiled or cemented doublet the laser will simply disappear as it goes from the glass lens into the CaF2 (or vice-versa if the CaF2 lens is in front). If it is air-spaced you will see the glass and two little "blips" from the coatings on the CaF2 but nothing in between the blips. That is what I see in the Kowa Highlander.
Thanks, Milt
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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The front element faintly shows the front edge as the glp touches the coatings then it dissapears. Then there is a single blip at the front surface of the second element, then the green shaft thru that element and then the blip as it exits the second element. That's it, no more.
I agree with Peter, there was no evidence that the Tak was anything other than a flourite doublet.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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pcad
Carpal Tunnel
Reged: 01/17/05
Posts: 1767
Loc: Connecticut
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I'll reconstruct my earlier post.
I checked the "pedigree" of the WO and Tak binoculars. Since both are based on existing telescope designs, the typical specs of focal length and ratio are "public knowlage". I've also talked about these binos with WO and Tak while at NEAF shows.
The WO 22x70 APO is based on their ZenithStar 70mm ED scope. The objective specs are 70mm, FL 430, f/6.2 FPL-51 doublet. Their earlier prototype 66mm ED binocular was based on their popular 66mm ED telescope. Its specs were 66mm, FL 388mm, f/5.9 FPL-51 doublet.
The Tak 22x60 Astronomer is still described on the Tak website. They state the objectives are 60mm Fluorite doublets with a focal length ratio of f/5.9. If you look at the complete specs there is an odd description of its optical design. It reads "Fluorite APO, 4 element, 3-groups". From conversations with Tak representatives at NEAF, the Astronomer objectives are the same as those in their FS-60C telescope. The telescopes specs are 60mm, fl 355mm, f/5.9 Fluorite doublet. The 4 element, 3-groups sounds suspiciously like an eyepiece description. On inspection with a GLP there's no evidence of anything other than a Fluorite doublet in front of the prisms.
The short story is that the WO is a f/6.2 FPL-51 doublet and the Tak is a f/5.9 Fluorite doublet. Of course there can be some variation in each instrument from the published specs.
Since Ed is using my 22x60 he's in a better position to describe what the GLP shows. My recollection is that the beam disappears in the Fluorite element.
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Peter
Telescopes 25 - 318 mm
Binoculars 15 - 88 mm
Microscope 50x - 1000x
Edited by pcad (07/09/09 08:40 PM)
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milt
professor emeritus
Reged: 09/13/04
Posts: 551
Loc: Arizona
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Ed & Peter,
Yup, it's true fluorite crystal - only difference from the Highlander is that it's used for the front lens instead of rear. The reason I asked is that in some later Takahashi fluorite scopes (I forget which) they used some mystery material in which you could still see the laser beam; i.e. they scattered some light. Glad to hear the 22x60 is the real deal - it's a shame they discontinued it.
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Clear skies, Milt
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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a special double with three 22x binocs.
Nice night tonight so I've been out on the deck all night. Little by little I ended up with 4 tripods outside. I was looking at the doubles in Lyra, and at M57, and then thought of a challenge for these three 22x binoculars.
first I scoped 100 Herc in all three, but it is so wide (14") for this power, it was really just for focusing. Then I turned to:
95 Hercules 18h+22 a nearly perfect equal very close double, 5.0-5.1/6.3"
In the Tak, very tiny pinpoints with a definite space, clear dots
In the WO, points slightly enlarged but a hint of a dark space
In the GO, points definitely large dots, merged but can still notice quite readily it's two.
These are probably three of the best binocular views of 95 Herc I've ever seen. I know I've split it using my Oberwerk 25x100. Must have seen it in my BT100, but probably at a higher power.
Look outstanding in the Tak.
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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field sharpness of the three compared on same double star
100 Herc is an even 14.2 arcseconds.
in the Tak, I could see it at 85% out, or 1.9° out of 2.2°
in the WO, I could see it at 70% out, or 2.1° out of 3.0°
in the GO, I could see it at 65% out, or 2.0° out of 3.05°
I was pretty impressed with the edge view in the Tak, but it's the WO that gives the widest very sharp fov. This star is giving about 300 arcsec, so this is easily still pretty good view.
I saw this star at 60% out in the Fujinon 16x70, and also I saw this star at 70% out in my long gone 20x80 Oberwerk Standard. That one is quite a long focal length, f/4.7 if I recall.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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lack of protection for eye glasses
Both the GO22x85 and the WO22x70 have very short usable eye relief. So I need to squinch up tight behind them to see the entire fov. I need the eye guard to be folded down. But by doing so, on both eyepieces the metal rim of the eyepiece is exposed at the surface. I heard it several times last night, that little click/clack noise. My eyeglasses were coming in contact with that metal rim. It's not a good noise.
The Tak rubber eyeguard extends over the metal rim on the eyepieces and does not present this problem.
The GO and the WO are NOT eyeglasses friendly binoculars. You won't have any problems if you plant yourself square behind the binocular and look straight in without ever tilting your head a little to either side. The bridge of your glasses between the two eyepieces will hit the rubber on the inside edges of the eyepieces, and the curved surface of your eyeglasses will be up and away from the metal edges. But as soon as you tilt slightly to either side or press close to see the entire fov, your eyeglasses may come in contact with that metal rim. There is no way to avoid it, it is right at the surface, not recessed at all.
This is bad. I've been thru this before. It doesn't show up after one or two uses, but after repreated use it will show up. It won't take too long before I have little scratches all over the front of my eyeglasses. If I continue to view thru these binoculars without adding some kind of protection over that metal, I am going to ruin my very expensive eyeglasses.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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pcad
Carpal Tunnel
Reged: 01/17/05
Posts: 1767
Loc: Connecticut
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I think it's worth pointing out that these oculars are found on other series 8 binoculars. Each objective size comes in two magnifications. The higher mag of each size uses these eyepieces. The lower mag versions use a longer FL, longer eyerelief eyepiece and may be more compatible with eyeglasses.
Long ER are the 7x50, 10.5x70, 15x85, 20x110
short ER are the 10x50, 15x70, 22x85, 28x110 and the WO 22x70
It seems that most people choose the higher mag versions, but I've heard good things about the lower mag versions also.
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Peter
Telescopes 25 - 318 mm
Binoculars 15 - 88 mm
Microscope 50x - 1000x
Edited by pcad (07/12/09 03:02 PM)
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BobinKy
Carpal Tunnel
Reged: 04/27/07
Posts: 1682
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Now where do we get those Tak 22x60s? 
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Bob
38°N
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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I'd recommend to Peter that he NOT sell his.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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Wes James
Post Laureate
Reged: 04/12/06
Posts: 3450
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Quote:
I'd recommend to Peter that he NOT sell his.
... And anyone else fortunate enough to own a pair! Funny- there's been 2 for sale in the past month- and have seen no comments here on either pair.
Guess we've been scared off from mentioning anything on here about anything for sale anywhere... 
Wes
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pcad
Carpal Tunnel
Reged: 01/17/05
Posts: 1767
Loc: Connecticut
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The only places I've seen them available is in the CN Classifieds, CN Shop and Swap forum and Astromart. I've noticed them for sale about 6 times in the last year and a half.
I bought mine on Astromart after two failed attempts with previous sellers. Strangely enough my pair had been sold to someone else who returned them due to a small cosmetic blemish. Go figure. 
Ed, I think I'll take your advice on holding onto them.
Edited by pcad (07/11/09 01:11 AM)
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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Quote:
Guess we've been scared off from mentioning anything on here about anything for sale anywhere...
Wes
no need to be scared
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
Edited by EdZ (07/11/09 09:54 AM)
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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tried to measure USAF resolution this morning.
I was all set up on my deck. I have a res chart pinned to a telephone pole about 100 yds away. Problem was I couldn't focus the GO22x85. I ended up moving further back, all the way thru my front yard, across the street and half way up my neighbor's drive way. Turns out the close focuse for the GO22x85 was about 175 yards.
The GO22x85 right eyepiece would not focus to as fine a reading as the left eyepiece. It's possible I needed to move back to 200 yds., since the right eyepiece was at the end of rotation and the left eyepiece had room to turn thru best focus. This is going to require moving my chart.
The Tak recorded the best resolution. Actually, quite impressive. At 88 yds., I could see both vert and horz bars to get 3.23 arcseconds resolution. That puts the Tak among the top very few binoculars I've tested. It also correlates very well with what I saw in splitting extreme close doubles.
The WO was very close to the Tak. Whereas the Tak could see both H & V bars for 3.23 arcsec, the WO could only see the horz bars at that level. It could see both H & V bars for 3.62 arcseconds res, the next step down. Still a very good reading, better than any other 20x80 I've tested.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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BobinKy
Carpal Tunnel
Reged: 04/27/07
Posts: 1682
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The close focus on my Garrett Signature 22x85 tested about 275 ft--give or take 100 ft. I made the estimate when I purchased them two years ago. The distance was not measured--just eyeballed. At the time my longest tape measure was 25 ft. And now, I really do not see the point of an accurate close focus with this model. Another issue--How to explain measuring the street to the neighbors?
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Bob
38°N
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James S
member
Reged: 07/10/08
Posts: 57
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Quote:
Another issue--How to explain measuring the street to the neighbors?
Tell them you suspect your land boundary should be in their backyard according to county record. 
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Rick
Post Laureate
Reged: 04/12/05
Posts: 3044
Loc: Tokyo, Japan
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Quote:
Another issue--How to explain measuring the street to the neighbors?
Laser rangefinders are relatively cheap and very accurate for distances over 5m.
cheers,
Rick
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www.japanastro.com
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Gary Fuchs
scholastic sledgehammer
Reged: 05/22/06
Posts: 867
Loc: Easton, PA, USA
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Edz,
I don't know if I've posted here before so will apologize for just jumping in.
I've been thinking about large aperture, low mag binos for some time and check them out whenever possible at NEAF and Stellafane or wherever.
This has been an interesting thread and seemed to be a very detailed review and careful comparison of various technical aspects as well as valuable subjective impressions - which in some ways are the most meaningful to me.
I gather that all will provide pleasing views and have no significant mechanical or optical weaknesses. I suppose that close focusing issue could be significant but as far as I'm concerned, not a problem. Maybe for very specialized birders?
The eyerelief matter is always a concern for me; but it seems that no matter how deep, I end up taking my glasses off anyway.
Question: In terms of value, dollar for dollar, how would you rate the WO 22x70's offered by Wes James here compared to the others?
I ask because I always keep an eye out for equipment at good prices offered by reputable people and in this case lack the technical expertise to make the judgment.
Thanks,
Gary
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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This WO22x70 may be the same as Wes's. Wes's I think was first off the line. This one came along after production.
The 22x70 is very good. Although smaller aperture, it has better image quality than the GO22x85. The WO22x70 has better resolution, sharper defined image dot quality, narrower fov BUT overall wider sharp outer field of view, better off-axis illumination, a larger center area of the objective fully illuminates the image. It's got a higher price tag, but it's got a lot going for it. It's worth more, I won't guess how much more. Neither beats the Tak.
I haven't really been able to test the differences in the aperture. But if 70mm is the right aperture for you then the WO22x70 is a very good one to have.
I suspect I'll see the full 85mm aperture prove to be substantial at times. Keep in mind too that my GO22x85 used cost only half of what the WO22x70 cost new.
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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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94bamf
professor emeritus
Reged: 12/15/08
Posts: 705
Loc: Kansas City,Mo
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EdZ, what do you think of the GO 22x85 compared to the GO signature 15x70 image quality wise? Overall quality wise?
Do you think the GO 22x85 is worth the extra cost compared to a set of the GO standard 25x100 bins? I keep debating about getting the signature 15x70's or just getting some 25x100's. Is the image quality in the Signature 15x70's worth more than the added apperture and mag in the 25x100's or the 22x85's for that matter? Which would you buy if you had no binoculars and only around $500 to spend? 
Ken
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Telescopes:
Celestron C6 SCT on CG4 mount
Skywatcher 8 inch F/5 Newt on a GEM
Celestron 8 inch Starhopper Dob
Celestron Oynx 80ED
Celestron C130 Mak
Celestron C102HD
Binoculars:
Nikon 7x35 Action
Nikon 7x50 Action
Zen Ray Summit 10x42
Celestron 10x42 Noble
Orion 10x50 Scenix
Celestron 10x50 Noble
Pentax 12x50 PCF WP II
Celestron 15x70 Skymaster
Oberwerk 20x60
Zhumell 20x80
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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If I wanted the widest fov, I'd get the 15x70.
If I wanted the larger aperture, it's a toss up, but I think I'd get the 22x85 over the 25x100.
My 25x100 is the Oberwerk 25x100 IF. It has much longer eye relief and better outer edge field sharpness. But the 22x85 has better illumination and ultimately a wider sharp fov.
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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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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Limiting Magnitude
during viewing last night I made numerous attempts throughout the night to reach the limit of magnitude.
Faintest star see naked eye was 5.05
The Tak 22x60 did not see any mag 11 stars. It could see mag 10.73 easy and mag 10.83 OK.
The WO 22x70 glimpsed 11.05 averted, maybe 3 times. Saw mag 10.73 easy and 10.83 OK.
The GO22x85 saw mag 10.73 readily, mag 10.83 easily. Near the mag 11.05 stars is also an 11.04, both seen numerous times averted. Mag 11.05 was seen direct a few times. Tried without success to see 11.17 and 11.18.
So the GO22x85 could see 0.2mag deeper than the Tak 22x60 and could see those stars easier than the WO22x70.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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BobinKy
Carpal Tunnel
Reged: 04/27/07
Posts: 1682
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Edz...
The limiting magnitude (LM) test produced some interesting results. Since I like to play around with LM, here are a couple of questions for you? (I hope you do not mind?)
The last time I tested my Garrett Signature 22x85 was under 5.5 NELM skies. On that night they delivered 11.4 LM. Does LM keep in step with changes of NELM? If NELM drops -0.4, will LM also drop -0.4?
What about altitude of the stars you measured? My 11.4 LM was at 70° altitude, the highest that I normally go with my Manfrotto 3246 tripod/501 head setup. I do not seem to get as much LM when I drop to 30° altitude--maybe decrease in LM of -0.3, -0.4, or more. I am not sure because this is something difficult for me to measure, depending upon which stars are out at the time I do my measure. What is your experience with altitude?
Thanks for running the LM test.
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Bob
38°N
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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In step? yes to some extent, so a fair generalization is to say yes.
Altitude has a significant impact of sky. At 30° you might see sky NELM of mag 5.0, whereas at 70° on the same night at the same time you migth see mag 5.5. Expect BLM accordingly.
Read this
CN Reports: Binocular Reports
CN Report: Limiting Magnitude in Binoculars
[CN Report] | 09/03/03 | by Ed Zarenski
What exactly is the limiting magnitude of a pair of binoculars? Does it depend on the size? The magnification? . . .
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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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94bamf
professor emeritus
Reged: 12/15/08
Posts: 705
Loc: Kansas City,Mo
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Edz, you will have to forgive me for being a suck-up, but I feed this needs to be said. If you don't mind, I was wondering what your profession is. I throughly enjoy reading just about anything you post on binoculars, your testing and reports are first rate. I was just wondering if you do this professionally? If you don't, you should.. You really make this place interesting..  
Ken
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Telescopes:
Celestron C6 SCT on CG4 mount
Skywatcher 8 inch F/5 Newt on a GEM
Celestron 8 inch Starhopper Dob
Celestron Oynx 80ED
Celestron C130 Mak
Celestron C102HD
Binoculars:
Nikon 7x35 Action
Nikon 7x50 Action
Zen Ray Summit 10x42
Celestron 10x42 Noble
Orion 10x50 Scenix
Celestron 10x50 Noble
Pentax 12x50 PCF WP II
Celestron 15x70 Skymaster
Oberwerk 20x60
Zhumell 20x80
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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Diffuse Objects and edge light loss
M71 can be seen in the Tak all the way to the edge whether positioned at top, bottom, left or right.
M71 in both the WO and the WO can still be seen at the edge when move to top or bottom, but when moved to left or right, is lost in the last 10% of the fov.
North America nebula section along east cost (the only portion that stood out as potential nebula) appeared brighter in the Tak than either of the other two binoculars. It appeared brighter in the GO85 than in the WO70.
In genral however, faint diffuse objects were a bit easier to find in the GO85. For instance a faint mag 9 globular NGC 6712, just below M11, was seen by all three, but was easier spotted with the GO85. I'd still like to compare these all on numerous more nebulae.
FWIW, objects were always perceived as larger in the Tak60. The much narrower field of view cropped out significant sky background and presents each target in a smaller window. When going back and forth from the larger fov GO85 to the smaller fov Tak60, always for a few seconds my impression was that the object appeared larger in the Tak. Illusion only.
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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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BobinKy
Carpal Tunnel
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Posts: 1682
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Quote:
North America nebula section along east cost (the only portion that stood out as potential nebula) appeared brighter in the Tak than either of the other two binoculars. It appeared brighter in the GO85 than in the WO70.
EdZ, any thoughts on why North America nebula appeared brighter in the Tak?
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Bob
38°N
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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Quote:
Quote:
North America nebula section along east cost (the only portion that stood out as potential nebula) appeared brighter in the Tak than either of the other two binoculars. It appeared brighter in the GO85 than in the WO70.
EdZ, any thoughts on why North America nebula appeared brighter in the Tak?
? better contrast
? I was looking at the area of the NA neb that is really an extremely dense star field and the Tak defines stars to a finer pinpoint, so the area looked like a brighter mass of points
? the Tak has a darker background
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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BobinKy
Carpal Tunnel
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Posts: 1682
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EdZ...
Thanks for doing the North America nebula test. And thanks for offering your thoughts on the Tak's performance.
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Bob
38°N
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BobinKy
Carpal Tunnel
Reged: 04/27/07
Posts: 1682
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Williams Optics drops price on new display model of 22x70mm APO Binocular .
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Bob
38°N
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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Quote:
Williams Optics drops price on new display model of 22x70mm APO Binocular .
they also dropped the price on the new fully boxed.
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14716
Loc: Cumberland, R I , USA42N71.4W
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To illustrate the very first post in this review, here is a series of photos looking thru these 22x binocs. The edge of objective is lined up with the edge of internal baffle or prism stop, whichever hits first. Notice the size of clear view thru and out the back end. This mimics the measurement one gets when checking for full illumination. The Ultra and the Signature are fairly typical of very good binoculars. All four of these in the top 15% of all measured. 60 out of 70 binoculars DO NOT have as great a degree of illumination as any of these four. Look at the difference between them from smallest to largest.
Upper left Oberwerk Ultra 15x70
Upper right Garrett Signatiure 22x85
Lower left William Optic Apochromat 22x70
Lower right Takahashi Astromomer 22x60
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EdZ
Professor EdZ
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For clarity here is a larger image of the Tak 22x60
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Mark9473
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Many thanks EdZ for showing such a clear illustration of something that you have mentioned so often on this forum, yet is not so easy to grasp (at least to me).
Checking out my Docter 15x60 that were here beside me, I get something that looks like the one at top left.
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Mark
Leica 8x20; Vixen 8x42; Swift 8.5x44, 10x50 and 20x80; TS 7x50; Orion 15x63; Docter 15x60
WO Megrez II 80 FD + Baader 90° T2 Amici
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Man in a Tub
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 By golly, I think I've got it!
Or thanks, I needed that!
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Todd
Brunton Eterna 15x51 ° Garrett Optical Signature Series 15x70
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EdZ
Professor EdZ
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Internal Baffles
The GO22x85 (left) and the WO22x70 (center) have no internal baffles. they do have finely ribbed sides inside the barrels which helps control reflection off the insides of the barrels. Note the Tak 22x60 Astronomer (right). It has three internal baffles sized to allow the light cone to pass but to block any stray light rays, eliminating reflections and stray light.
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RichD
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That's a good shot, I remember seeing pics of the internals of a Tak on here a while back and being struck by the baffle rings - I hadn't seen a bino with internal construction like that before.
I believe that kind of baffling is quite common in refractors (which is what the Tak is).
You have to wonder why more manufacturers don't use similar baffle rings to increase contrast - space restrictions?
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Clear skies
Rich
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GlennLeDrew
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1) Most bino barrels are already so tapered that there's just no room to fit in even very annularly narrow baffles. Hence the more common 'ribbing.'
2) EdZ; The photo loking through the Oberwerk Ultra 15X70's objective, showing the partially clipped image produced by the eyepiece, suggests a possible lack of full illumination on axis. Could you verify this? I do this test by first aiming the bino so that some prominent object is well centered in the image produced by the eyepiece. Then when I move laterally until the sight line toward this object is just intercepted, I check to see what's causing the blockage. If it's an internal stop (most often the front prism aperture), I then make an estimate of how much of the objective's edge is not contributing to image formation. I'll do this for a total of four sight lines; left, right, top and bottom. You'd be surprised how many binos will reveal asymmetry here!
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Home-made 11X50 right angle bino, 8.1 deg. FOV
Modified 26X100 bino, 3.5 deg. FOV
Home-made Mk II RA bino, using interchangeable objectives and eyepieces
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EdZ
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Glenn,
I do that test with a target laser. Actaully I've been measuring and writting about the assymetry for maybe 6-7 years. The target laser method is documented(perhaps in this thread) pictorally. Previously, there have been hundreds of posts discussing the method. You'll see I refer to that measure as tilt. FWIW, the Ultra is only slightly assymetric. The GO Signature is more assymetric than the Ultra. Even the WO is off a little. The Tak is dead center.
edz
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GlennLeDrew
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Ed,
Gotcha! But to my question, slightly modified... Is the Obie Ultra 15x70 working at full aperture (and when considering asymmetric illumination if warranted)?
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Home-made 11X50 right angle bino, 8.1 deg. FOV
Modified 26X100 bino, 3.5 deg. FOV
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EdZ
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Essentially the Obie Ultra 15x70 is operating at full aperture (69+), and the full illumination is 40%. Also it has a very minor 2-3% tilt in one barrel and 7% tilt in the other barrel.
edz
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EdZ
Professor EdZ
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Short observing session with GO22x85 this morning. 4:30 to 5:30 am. At 5am faintest star naked eye visible was mag 5.45. In M45, I observed stars of mag 11.3 direct and mag 11.5 averted. That's the deepest I've ever gone with the GO22x85.
OC 2194 in the upraised arm of Orion was seen as a very faint diffuse spot. M1 and M78 were fairly bright and pretty large. M33 was very large. Gamma Aries 7.8" was seen split, but not easily. Searched for M74 and suspected seeing it averted two or three times. M37 was somewhat resolved, perhaps 20-30 stars. NGC 2157, near M35, was seen as a diffuse spot.
Searched for IC342 in Camelopardalis, but did not see it. On the way to it, all the way from Cassiopeia thru Perseus, I caught NGC457 the Owl and saw the faint diffuse spot of nearby 436, also saw M103, NGC 659, 653 and 654, Stock2, Double Cluster, OStf26, NGC1502 and Stf485 within. At the other end of Cas, NGC7789 was a large diffuse glow, and the only cluster I could make out in the recent area of intense study was NGC7790. Probaly about 10-12 scattered stars around the area of 7788. Found NGC129 half way between gamma and beta cas.
Other clusters seen: M38, NGC1907, M36, NGC1662 in Orion shield, 1807 and 1815 in Taurus above the shield, 2169 the 37 cluster, 2264 the Christmas tree cluster, Stf 953 a 7" pair below the Christmas tree, and 2244 the cluster at the center of the Rosette neb.
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BobinKy
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EdZ...
Nice report of the your observation with the Signature 22x85. A couple of mornings ago I observed Taurus and Orion with the Fujinon FMT-SX 7x50. The Hyades fits perfectly in the 7x50's 7.5° eyecups. The seasons--they are a' changing--and the change is good. Nothing energizes observing like the constellations Orion and Taurus!
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Bob
38°N
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Wes James
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Quote:
The seasons--they are a' changing-- and the change is good. Nothing energizes observing like the constellations Orion and Taurus!
I agree! One morning this week on my way to work at 5:45 a.m., I looked up to see a beautiful crystal-clear sky, Orion, a beautiful crescent moon adjacent to the brilliant jewel Venus- after such a lousy summer of hazy, humid, overcast skies, it was like a breath of fresh air- and hope for some good observing once again- finally!
Wes
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mooreorless
Just worried
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Same thing here Wes and Bob. Nice change for sure.:-)
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EdZ
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Sunday morn 9-20 Sky LM 5.5. temps 45°. 4:30 to 5:30 am. At 5am faintest star naked eye visible was still mag 5.5. (the star was 57 Tau). Sky conditions were identical to my brief session two days ago.
This short observing session with WO22x70 parallels the brief session I had the other morning with the GO22x85. In M45, I observed stars of mag 11.3 averted (A18e) and mag 11.5 averted (A18d), however, I only glimpsed A18d twice and after about 5-10 minutes of trying could not see it any more than just those glimpses. It was easier to see it the other day with the GO22x85, when it was seen averted and each time for several seconds at a time. Just as with the GO22x85, this is the deepest I've ever gone with the WO22x70, however it was easier to see mag 11.5 with the GO22x85 than with the WO22x70.
The "7" in NGC2169, the 37 cluster, was quite prominent. Nearby OC NGC2194 in the upraised arm of Orion was seen as a faint diffuse spot although fairly large, perhaps as large as the "7". M78 was pretty bright in comparison. NGC 2194 was similar to M1.
M33 was very large. I mistakenly reported the other day (in the deep sky forum) that I thought M33 filled about 1/3 of my 3° fov. I would say it filled no more than 20-25% of my fov.
Gamma Aries 7.8" was seen split, quite easily in the WO. It was more difficult in the GO. Searched for M74, however I did not positively detect it.
Searched for IC342 in Camelopardalis, but did not see it. Unfortunately, when I returned inside and consulted my charts, I'd found that I was concentrating my efforts about 1° away from the correct spot. Should have taken the charts out with me!
In the area from Cassiopeia to Perseus, I easily saw M103, NGC 659, 653 and 654, Stock2, Double Cluster, OStf26, NGC1502 and Stf485 within.
At the other end of Cas, NGC7789 was a large diffuse glow (perhaps 10-15 stars), and the only cluster I could make out near NGC7790 was 7790. However, I did see about 10 scattered stars around the area of 7788.
I saw NGC2264 the Christmas tree cluster and Stf953, a 7" pair below the Christmas tree. This pair is a bit closer and much fainter than mesartim and was considerably more difficult, although it did appear split in the WO, as compared to in the GO22x85 where I would say it appeared elongated but not cleanly split.
All four components of the Trapezium were cleanly separated even perhaps 30-40% off the center axis. But by 60-70% out, none of the Trapezium stars could be seen individually.
I observed Sirius, Betelgeuse, Rigel and Venus looking to instigate false color and even moving these to positions well off-center could not see any false color. Betelgeuse was a distinct orange.
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Philip Levine
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Hi Ed,
I've been following this thread, since I recently purchased a GO SS 22x85.
I have the following question, would the GO SS 15x85 generally show sharper viewing of stars/open clusters, and further out from center, than the GO SS 22x85?
thanks, Phil
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EdZ
Professor EdZ
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Sorry, can't answer. I've never used the 15x85.
edz
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pcad
Carpal Tunnel
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Ed,
Phil's question is partly related to the differance between the low and hi power oculars available in this series of binoculars. Would comparisons between the 7x50 and the 10x50 be valid for the 85mm binoculars?
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Telescopes 25 - 318 mm
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EdZ
Professor EdZ
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possibly not, as eyepieces act differently as f# varies, and I don't know if the f#s would be similar. Also, I don't know for certain if the eyepieces are the same, and I've never tested the 10.5x
edz
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DaveL
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According to the Garrett website the focal ratios for this series are as follows:
50mm: f/3.7
70mm: f/4.0
85mm: f/4.7
110mm: f/4.7
It also says that the 50mm & 70mm have two element objectives in one group, whereas the 85mm and 110mm have two elements in two groups.
The ratio of the low to the high magnifications in this series are 0.70, 0.70, 0.68 and 0.71 , which, assuming the specified magnifications for the larger binoculars are rounded to the nearest integer, is certainly is consistent with the idea that the same eyepieces are used for all binos in this series.
-Dave
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pcad
Carpal Tunnel
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Ed,
I meant the WO 7x50 compared to the series 8 10x50. I thought you had looked through a sample of both at some time.
The 10.5x is the low power version of the 15x70 series 8 binoculars. I realize you haven't looked through those.
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Peter
Telescopes 25 - 318 mm
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EdZ
Professor EdZ
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well generally, shorter eyepieces are better corrected than longer eyepieces. BUT that's really general. There are examples where we might find shorter eyepieces not particularly any better than the longer ones.
Given the f#, the sets would be powered by 26.6mm and 18.7mm eyepieces. (The 22x85 was found to be less than 22x, and the 15x70 was found to be less than 15x, so the short eyepiece is probably more like 18.9mm, and this would agree with the actuals I've measured for that eyepiece sequence).
For ease of discussion lets call them 27mm and 19mm.
We might expect that the higher powered within the sets would be better corrected. I've never had a set in any given aperture size, but I've used the 7x50 (27mm), the 15x70 (19mm) and the 22x85 (19mm).
By actual measures, the 7x50 and the 15x70 were similarly well corrected. Both were better corrected than the 22x85. Unexpectedly, the longest eyepiece in the slowest binocular showed one of the best corrections, unless of course the WO7x50 is not of the same breed and in not using the same components. No real way to tell. Not what we would expect, but that's how they measure.
I've also used the WO22x70, which may be the best corrected of all of these.
edz
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Edited by EdZ (10/06/09 10:53 AM)
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