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btschumy
Vendor - Southern Stars


Reged: 04/13/04
Posts: 1708
Loc: Longmont, CO, USA
Takahashi 22x60 vs the Oberwerk 20x90
      #194725 - 09/12/04 11:39 AM

For a while I have been curious about the Takahashi 22x60 binoculars. Today I was lucky enough to borrow a pair from a friend so I could compare them to my Oberwerk 20x90 binoculars. I also set up my Nikon 10x42 SE's along side them although it was hard to compare binoculars that are so disparate. All three binoculars were tripod mounted.

DAYLIGHT PERFORMANCE

I first started making some comparisons in the daytime. It was the heat of the day so there was a fair amount of thermal activity that made critical comparison difficult.

First off let me say that the 22x of the Taks is a quite noticeable increase over the 20x of the Oberwerks. I hadn't expected this but it was definitely apparent through the eyepieces. I suspect that some the increased sharpness of the Taks mentioned below may in fact be due to the higher power.

I need to were glasses to observe with exit pupils > 1 mm. I could see the full field of view in both the Taks and the Obies, but the Obies had a bit more comfortable eye relief. In the Nikon SEs, I couldn't quite see the field stop all the way around, but the cutoff was very minor.

Looking down the barrels from the objective end, you could see that there was very little if any vignetting in the Taks. The exit circle could be fully seen with your eye right next to the edge of the objective. In the Obies, you start to get some cutoff about 1/2 way to the edge of the objective. By the time you get to the edge, only about 1/8 of the exit circle was visible. Some pretty significant vignetting here. The Nikons were intermediate between these two.

Although I didn't really have any high contrast object to look at during the day, I really didn't notice any Chromatic Aberration (CA) in any of the three glasses. I tried looking carefully but it was not there today. This may have been in part because it was somewhat overcast.

I carefully looked at a banner hanging on a building several miles away. The lettering was slightly easier to read in the Taks vs the Obies. I believe this was partly due to the increased magnification and partly due to an inherent step up in sharpness. As I moved the banner towards the edge of the FOV in the Taks, I was surprised to see the lettering start to fuzz about 2/3 of the way to the edge. I had always heard the Taks were pinpoint to close to the edge, but I wasn't seeing it here. In the Obies, I noticed degradation starting about 1/2 the way to the edge. The Nikon SE's were similar to the Taks in being sharp until 2/3 of the way to the edge. They both degraded gracefully after that.


CHROMATIC ABBERATION

As dusk approached, some bright freeway lights away in the distance turned on. Examining them carefully, I could see no CA in the Taks (as I would expect with Apos and relatively low power). The Obies showed moderate CA and it was highly dependent on eye placement. It was possible to find eye positions that really minimized the CA, but almost impossible to hold it there. I didn't notice any CA in the Nikon SE's.


NIGHTTIME PERFORMANCE

Later, after it got dark, I came out again to test the binoculars under the stars. It was a pretty bad night as far as transparency but I was most interested in performance on stars, not extended objects, so it didn't really matter. I would estimate the limiting magnitude was between 3.5 and 4.0.

In order to evaluate sharpness, I looked at Gamma Delphinius and Eta Cassiopeiae. The former is a 4.5/5.5 pair separated by 9.6". The latter is a 3.5/7.5 magnitude pair separated by 12".

Gamma Del was split by both the Taks and Obies. However, the spit was considerably cleaner in the Taks. Moving the double towards the edge of the field in both binoculars confirmed what I'd found in the daylight. The Tak's image held up almost unchanged until about 75% of the way to the edge. Even almost right on the edge you could still see the star(s) as elongated. In the Obie 20x90s, the split was less defined in the center of the field and by the time you moved about 50% of the way to the edge, I could no longer see it as double.

Eta Cass, even though it has a wider separation, was harder due to the magnitude disparity of the components. the Taks did a nice job on it and I could barely (but crisply) see the fainter companion sitting next to the primary. The Obies were just not up to the task on this one. I could not see the secondary. It was lost in the glare and flaring of the primary.

While looking at these doubles (and a few other star fields I examined), it was apparent the Obies were seeing deeper than the Taks. This is not unexpected given the 30 mm aperture advantage. However, the Obies did not blow the Taks away here. I assume this is in part due to the Taks unvignetted field and its better contrast. I would estimate I was seeing 1/4 to 1/2 magnitude deeper with the Obies.


CONCLUSIONS

The Taks were clearly superior optically. That's to be expected given they used the same objectives as on the Takahashi short focal length APO refractor. However, I was a bit surprised that the edge performance wasn't quite as good as in a APO telescope. I used to have the Tak FC60 mm F/7 refractor and I remember the edges being cleaner than they were in the binoculars.

I was also a bit surprised that the flaring around bright stars was not totally eliminated in the Taks. I seem to see this in every pair of binoculars I have looked through. I would suspect this an optical aberration in my eyes or in my glasses, but I do not see the same thing using low powers (28x) with my TEC 140 Refractor. I see the flares even if I use the binoculars with one eye so it is not a one eye vs two thing. Given the Tak objectives are probably beyond suspicion, I am forced to suspect the flares coming from the porro prisms or from the eyepieces. It is indeed a mystery to me.

--------------------
Bill Tschumy
Southern Stars


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EdZ
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Re: Takahashi 22x60 vs the Oberwerk 20x90 new [Re: btschumy]
      #194789 - 09/12/04 01:11 PM

Very good information Bill.

Some interesting comparisons. I'll be adding this to our long list.

edz

--------------------
Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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KennyJ
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Reged: 04/27/03
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Re: Takahashi 22x60 vs the Oberwerk 20x90 new [Re: EdZ]
      #194817 - 09/12/04 02:19 PM

Great report Bill.

I'm pleased to notice the quality and regularity of such member reports seems to be on the increase of late , and as with Fiske's recent offerings , this was a rare insight into how three very different but popular models compare in certain situations at certain tasks.

The "problem" with edge performance with the Taks reminds me of my own dissapointment with my Zeiss 85mm Diascope , which has super-achromat status.

I'm also left wondering if it's the presence of prisms per se or a combination of that AND eyepiece distortion , but I'm leaning more toward the former.

For example ,it seems that Televue owners are not experiencing this problem , almost regardless of which eyepiece is in use.

But ,whatever the reason ,if a binocular of true APO status and with barely a 45 degree AFOV cannot remove this problem , there seems little hope for the rest :-)

Yet according to some , the Canon IS , not to mention several other models from various manufacturers , manage to offer "better" edge performance than 75% out from centre.

I'm also wondering if these oft -banded PERCENTAGE figures would benefit from more specific definition , for example , I wonder if EVERYONE who quotes such percentage figures is actually talking in terms of radius or diameter ?

I'm glad you eliminated the "one -eye" possibility.

On a related issue , earlier today during a "terrestrial session" with various scopes and binoculars ,I finally pin-pointed something which has been troubling me for some time.

I've discovered that I am suffering from "partial red colour blindness" in my left eye.

EVERYTHING I look at with my left eye , of a naturally reddish brown colour , when magnified , looks like a slightly grey , washed -out version of what I see through my right eye. It's not noticeable when looking at things with naked eye or with my glasses on , which correct for astigmatism , but is very evident when looking through binoculars and a scope with alternating eyes.

A search through "google" has led me to believe there is nothing I can do or have done about this -- it is just something I will have to live with.

At least the discovery has eased my concerns about my binoculars. It being a condition which shows itself more in direct proportion to increased magnification , unknown to me it must have been a factor in my thinking that my 15 x 70s were more "at fault" than my 10 x 50s , which again were more "at fault" than my 7 x 42s.

Previously , I'd put that down to relatively quality and related price differences between the three models in question , which co -incidentally , flow in the same order.

Anyway , I'm getting WAY off topic here.

Thanks again Bill for a very interesting report.

Regards , Kenny.

--------------------


Milton Wilcox R.I.P






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btschumy
Vendor - Southern Stars


Reged: 04/13/04
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Re: Takahashi 22x60 vs the Oberwerk 20x90 new [Re: KennyJ]
      #194829 - 09/12/04 02:37 PM

Quote:

The "problem" with edge performance with the Taks reminds me of my own dissapointment with my Zeiss 85mm Diascope , which has super-achromat status.

I'm also left wondering if it's the presence of prisms per se or a combination of that AND eyepiece distortion , but I'm leaning more toward the former.




It is indeed a mystery. I'll have to take another look through some Canon IS binos to check how I percieve the edge.

Quote:

I'm also wondering if these oft -banded PERCENTAGE figures would benefit from more specific definition , for example , I wonder if EVERYONE who quotes such percentage figures is actually talking in terms of radius or diameter ?




In my case it is a percentage of the radius. I would center the object and evaluate it. Then pick out the spot 1/2 the way to the edge and move the object to there and compare. Now locate the spot halfway from where I am to the edge and move the obejct to there. .... This gives me 1/2, 3/4, 7/8, ...

--------------------
Bill Tschumy
Southern Stars


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Re: Takahashi 22x60 vs the Oberwerk 20x90 new [Re: btschumy]
      #194837 - 09/12/04 03:03 PM

Bill,
Great report. I am surprised at your findings on the edge performance of the Taks. As Kenny says if a bino of this quality and spec is unable to remove this problem....

Its very interesting (as always) to see the Oberwerk so favorably compared to a bino many times its price. The price/performance ratio made painfully obvious once again.

Thanks for the post.


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btschumy
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Re: Takahashi 22x60 vs the Oberwerk 20x90 new [Re: ]
      #194886 - 09/12/04 04:39 PM

Quote:

Bill,
Great report. I am surprised at your findings on the edge performance of the Taks. As Kenny says if a bino of this quality and spec is unable to remove this problem....

Its very interesting (as always) to see the Oberwerk so favorably compared to a bino many times its price. The price/performance ratio made painfully obvious once again.




Yes, the Obies held up pretty well. However, as I said, the Taks were clearly better. Enough so that I am going to pony up for something better than the Obies. It probably won't be the Taks, but it might very well be something like Burgess's new Miayuchi 100 clone. I'm at least going to have Burgess ship me a pair so I can give them a serious look.

Not that I can afford them right now, but how do the Kowa Highlanders do at the edges, and how are they with the star flaring? Are they as pinpoint as an Apo telescope?

--------------------
Bill Tschumy
Southern Stars


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Anonymous
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Re: Takahashi 22x60 vs the Oberwerk 20x90 new [Re: btschumy]
      #194938 - 09/12/04 05:56 PM

Bill,
Even..as your review pointed out..the surprsing price/performance of the Obies, and which could be said of my own 11x70s, I too am going to get something better.

The Nikon SE seems like a logical choice, but id like something more than 12X. The Miyauchis and Taks, as we've discused before seem to me the next choice.

On the Kowas, check out the Astro-Mart bino forum. Youll find a long cascading thread about the Highlanders. There is specific discussion on edge performance and flaring....also 2 of my biggest concerns.

They are pricey, but the post is full of praise, though it is specific to the fluorite model, with less enthusiasm for the non-fluorite model.

If/when you (can) get the Burgess' id be curious to hear about them.


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Craig Simmons
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Reged: 12/10/03
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Re: Takahashi 22x60 vs the Oberwerk 20x90 new [Re: btschumy]
      #195232 - 09/13/04 07:41 AM

Quote:

In the Obies, you start to get some cutoff about 1/2 way to the edge of the objective. By the time you get to the edge, only about 1/8 of the exit circle was visible. Some pretty significant vignetting here.




I looked at my Obie 20x90s thru the objectives and the from the top at the edge and the exit pupil was vignetted about 80%, from the left, right and bottom edges it was about 50% to 60% vignetted.

--------------------
Craig Simmons
Oberwerk 8x56, 20x90
Nikon Action IV 10x50
Barska 15x70
Galileo 20x60
Stellarvue 15x63, 20x85
Orion XT10 pre-Classic
Antares 10
Stellarvue AT1010


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btschumy
Vendor - Southern Stars


Reged: 04/13/04
Posts: 1708
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Re: Takahashi 22x60 vs the Oberwerk 20x90 new [Re: ]
      #195256 - 09/13/04 08:40 AM

Quote:

On the Kowas, check out the Astro-Mart bino forum. Youll find a long cascading thread about the Highlanders. There is specific discussion on edge performance and flaring....also 2 of my biggest concerns.




Interesting. I have read through that thread relatively recently but didn't remember anything talking about edge performance or flaring. I'll have to go slog through it again and read a bit more carefully. Was the upshot that the Kowas were great in this regard, or do they also suffer from this syndrome?

--------------------
Bill Tschumy
Southern Stars


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btschumy
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Re: Takahashi 22x60 vs the Oberwerk 20x90 new [Re: Craig Simmons]
      #195294 - 09/13/04 09:36 AM

Quote:

I looked at my Obie 20x90s thru the objectives and the from the top at the edge and the exit pupil was vignetted about 80%, from the left, right and bottom edges it was about 50% to 60% vignetted.




Interesting. I just looked at mine and and the vignetting appears pretty symmetric all the way around. I'm no optics expert so don't get too concerned, but it sounds like you may have some minor alignment issues. Perhaps the tubes were not perfectly parallel and thus the prisms had to be adjusted significantly to re-collimate. I would think this might give the effect you are seeing.

--------------------
Bill Tschumy
Southern Stars


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EdZ
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Re: Takahashi 22x60 vs the Oberwerk 20x90 new [Re: btschumy]
      #195387 - 09/13/04 11:49 AM

This has more to do with the objective lenses not being in a perfect plane with each other. the barrels can be perfecly parallel, but the objectives, if seated slightly different in respect to each other, will throw the center of the optical axis off from the geometric center.

What you have observed in the 20x90, I also observed in the 22x100 and I wrote about this in the Vignette Thread.

The optical center of the image being delivered to the exit pupil is not in line with the geometric center. Optimum light is not in the center of the exit pupil. Optimum performance is not in the center of the exit pupil.

Take that 20x90 binocular and do a sharpness of image test using a close double star. Considering it's a 20x binocular you would need to use a pretty close double say 20" or 15". Now test that double along several lines that pass from one side of the view thru the center to the other side of the view. For example, test sharpness along a line from 10oclock thru the center to the edge at 4oclock. Then do the same from 2oclock thru 7oclock and 3 to 9 and 12 to 6. You will be surprised at what you find. based on what you saw in the down the tube visual inspection, it will not be symetric. It should be.

edz

--------------------
Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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craig_oz_land
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Re: Takahashi 22x60 vs the Oberwerk 20x90 new [Re: btschumy]
      #196918 - 09/14/04 11:08 PM

Quote:

........However, I was a bit surprised that the edge performance wasn't quite as good as in a APO telescope. I used to have the Tak FC60 mm F/7 refractor and I remember the edges being cleaner than they were in the binoculars.




Nice report Bill.

Could it be that the edge performance difference could be due to the slightly faster optics F5.9 Tak22x60 compared to F7 Tak FC60? The eyepieces are an unknown but I don't think Tak would have compromised the whole system with a bad eyepiece. Prisms as well?

I noticed the edge sharpness not being as good as I expected based on the reviews of the Tak 22x60. That said I think it is at the pointy end of the field.

There is CA (very slight but noticeable)in the Taks if you give it some hard targets.
To clarify the last paragraph, the CA is mainly due to eye placement. I did the test again and found that I could not detect any CA once my eyes were aligned with the eps.

However, again as above I would say it is at the pointy end of the field in that respect.

--------------------
Takahashi FS-102
Fujinon FMT-SX2 7x50
Takahashi Astronomer 22x60

Edited by craig_oz_land (09/15/04 10:35 PM)


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Anonymous
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Re: Takahashi 22x60 vs the Oberwerk 20x90 new [Re: btschumy]
      #196948 - 09/15/04 12:01 AM

Quote:

Quote:

On the Kowas, check out the Astro-Mart bino forum. Youll find a long cascading thread about the Highlanders. There is specific discussion on edge performance and flaring....also 2 of my biggest concerns.




Interesting. I have read through that thread relatively recently but didn't remember anything talking about edge performance or flaring. I'll have to go slog through it again and read a bit more carefully. Was the upshot that the Kowas were great in this regard, or do they also suffer from this syndrome?




Bill,
Yes that is the impression I came away with, but without specific posts to point you towards I cant back it up...
The upshot I came away with was the fluorite model was well corrected and superior overall with the regular model not being the same caliber.


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EdZ
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Re: Takahashi 22x60 vs the Oberwerk 20x90 new [Re: ]
      #197110 - 09/15/04 09:16 AM

Two things we can discuss here. We know something about the amount of vignette seen in the 20x90s and in my 22x100. It's non-symetrical in some. In Bill's 20x90 it seems to be symetrical. Bill, can you tell us what you see for vignette when looking into the 22x60s? This will have some affect on the light at the edges of the Tfov.

We know what the edge sharpness test seems to show. Not surprising. But some of the best binoculars do show significantly better sharpness towards the edges. Especially at higher powers. The BT100 at f6.2, with either 20mm TV plossls at 31x or 12.5mm UO orthos at 50x, is sharp right up to the very edges of the field stop. With these eyepieces, you can put a 7" double right up to the field stop and still obseve the two components cleanly separated. Generally this occurs with narrow fields of view which usually result from well corrected narrow Afov eyepieces, such as I referred to above. Bill, can you tell us what is the True field of view of the Taks? That will help determine what the Afov of the eyepieces is. Most binoculars use 60 to 65 WA eyepieces and hence show edge diostrotion. Fujinon 10x70s use 52 plossl eyepieces. Pentax, PCFs, famous for edge sharpenss use 45 and 42 orhto eyepieces.

If the Taks are f5.9 then the focal length is 354mm. Since there are 22x, then 354/22 = the eyepieces have a focal length about 16mm. If we know the Tfov of the binocs, we can determine the Afov of the eyepieces. If they are WA like 60 or so, it wouldn't be surprising at all to see some distrotion in the outer edges of the field of view. This might account for why, even though they use the same objectives as the scope, there seems to be greater distortion in the binocs. Normal if the eyepieces are WA.

edz

--------------------
Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21


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btschumy
Vendor - Southern Stars


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Re: Takahashi 22x60 vs the Oberwerk 20x90 new [Re: EdZ]
      #197139 - 09/15/04 10:03 AM

Quote:

Two things we can discuss here. We know something about the amount of vignette seen in the 20x90s and in my 22x100. It's non-symetrical in some. In Bill's 20x90 it seems to be symetrical. Bill, can you tell us what you see for vignette when looking into the 22x60s? This will have some affect on the light at the edges of the Tfov.




Ai I think I mentioned in my original report, there appears to be no vignetting in the Taks. I can place my eye right at the edge of the objecting and still see the entire exit pupil.

Quote:

Bill, can you tell us what is the True field of view of the Taks? That will help determine what the Afov of the eyepieces is. Most binoculars use 60 to 65 WA eyepieces and hence show edge diostrotion. Fujinon 10x70s use 52 plossl eyepieces. Pentax, PCFs, famous for edge sharpenss use 45 and 42 orhto eyepieces.




It is spec'ed at 2.1 degrees. I didn't measure it using stars in the sky, but compared to my 2.8 (actual) degree Obies, this seems about right.

Quote:

If the Taks are f5.9 then the focal length is 354mm. Since there are 22x, then 354/22 = the eyepieces have a focal length about 16mm. If we know the Tfov of the binocs, we can determine the Afov of the eyepieces. If they are WA like 60 or so, it wouldn't be surprising at all to see some distrotion in the outer edges of the field of view. This might account for why, even though they use the same objectives as the scope, there seems to be greater distortion in the binocs. Normal if the eyepieces are WA.

edz




If the TFOV is 2.1 and we are working at 22x, then the AFOV would be 46 degrees, so they don't appear to be WA eyepieces.

--------------------
Bill Tschumy
Southern Stars


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craig_oz_land
sage


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Re: Takahashi 22x60 vs the Oberwerk 20x90 new [Re: btschumy]
      #197917 - 09/16/04 03:30 AM

Quote:

Ai I think I mentioned in my original report, there appears to be no vignetting in the Taks. I can place my eye right at the edge of the objecting and still see the entire exit pupil.




From memory there is an extremely small vignetting from the first knife edge baffle.


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EdZ
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Re: Takahashi 22x60 vs the Oberwerk 20x90 new [Re: craig_oz_land]
      #198006 - 09/16/04 06:40 AM

Bill,

I'm surprised at your finding of little to no vignette, although it is entirely possible. I've done this test on two dozen binoculars and on one binocular, the BT100, with half a dozen different eyepieces in place. In about 30 tries, only once have I seen no vignette, that was in the BT100. With few exceptions, every other test shows vignette in the range of 30% to 100%. Fujinon 16x70s show about 80% vignette from the edge. Nikon 12x50SEs are about 50%.

I'm curious. Do you see any vignette when you look down the barrel of the 10x42 SEs?

edz

--------------------
Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21


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btschumy
Vendor - Southern Stars


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Re: Takahashi 22x60 vs the Oberwerk 20x90 new [Re: EdZ]
      #198071 - 09/16/04 10:10 AM

Ed,
I just went and looked again. Craig may be right that the first knife edge barely vignettes the very edge. I would guess no more than 5%, maybe less. Certainly not enough to be noticible.

I also looked through my 10x42 SEs. I would guess these vignette more than the 50% that you mention. It is really hard to estimate, but I'd say around 70%. The "cat's eye" you see at the edge was maybe twice as wide as tall if that helps at all.

--------------------
Bill Tschumy
Southern Stars


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EdZ
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Re: Takahashi 22x60 vs the Oberwerk 20x90 [Re: btschumy]
      #198108 - 09/16/04 11:00 AM

That seems reasonable for the 10x42s compared to my quick eyeball of the 12x50s.

These Taks seem to fall into the rarified category of little to no vignette. I thought at first that's not particularly surprising, considering the very narrow Afov. But not all the Afov binoculars fell into that group. the Pentax binoculars have ortho like eyepieces, yet they did not fare very well in the vignette test.

The BT100 has done better than any other binocular I've compared to date. It showed the least amount of vignette with the original equipment 10mm WA (62x) eyepiece as compared to 10 other eyepieces I used to test it. Some of the eyepieces tested include the 30mm Ultima, 26mm TV plossl, 20mm TV plossl, 18mm Meade SWA, 17mm Orion Sirius plossl, 14mm Radian and a 12.5mm UO ortho.

edz

--------------------
Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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Claudio
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Re: Takahashi 22x60 vs the Oberwerk 20x90 [Re: KennyJ]
      #198144 - 09/16/04 11:28 AM

Kenny,

You wrote:
"On a related issue , earlier today during a "terrestrial session" with various scopes and binoculars ,I finally pin-pointed something which has been troubling me for some time.
I've discovered that I am suffering from "partial red colour blindness" in my left eye.
EVERYTHING I look at with my left eye , of a naturally reddish brown colour , when magnified , looks like a slightly grey , washed -out version of what I see through my right eye. It's not noticeable when looking at things with naked eye or with my glasses on , which correct for astigmatism , but is very evident when looking through binoculars and a scope with alternating eyes."


If I use my terrestrial scope for long, I note similar problems in my eyes. Anyway they disappear after some time. Try to check your eyes when they are relaxed, and not after using binoculars or telescopes. I find that also the monitor of the PC is stressing for eyes.


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