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idahoman
sage
Reged: 11/25/05
Posts: 473
Loc: Idaho, USA
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This is my first post in the bino forum. So, I have some learning ahead of me. I just happened upon a pair of Oberwerk 25x/40x 100mm Classic binoculars at an estate sale. At 25 power, they seem great. At 40 x, however, I notice no gain. This seems to be a "common" complaint. Is there an easy fix to improve the viewing at 40x with these glasses? Thanks for your help.
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A Guy In Idaho
43° 31' N 112° 4' W
4780 ft elevation
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altalingua
newbie
Reged: 10/07/09
Posts: 1
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What do you mean by "no gain" ?
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idahoman
sage
Reged: 11/25/05
Posts: 473
Loc: Idaho, USA
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At 40x, the view seems soft. If I collimate, I worry that the 25x view will deteriorate. Is it the eyepiece? Should I buy the "interchangeable eyepiece" modification kit?
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A Guy In Idaho
43° 31' N 112° 4' W
4780 ft elevation
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idahoman
sage
Reged: 11/25/05
Posts: 473
Loc: Idaho, USA
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I am a bit surprised that there are not more people out there attempting astronomy with these. Other than the straight-through design and resulting neck ache, they have gotten quite favorable reviews. I am quite happy with them at 25x. Very little CA, and good sharp field. I was just hoping to improve the 40x viewing.
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A Guy In Idaho
43° 31' N 112° 4' W
4780 ft elevation
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Rich V.
Pooh-Bah
Reged: 01/02/05
Posts: 1395
Loc: Carson Valley, Nevada, USA
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I have no experience with these; has Kevin at Oberwerk indicated that others feel that the 40x eyepieces are "soft" as well? What targets are you looking at? Why do you feel collimation may have something to do with it?
It doesn't seem to be asking too much to expect sharp views at 40x from a 100mm binocular. The interchangeable eyepiece modification sounds interesting; providing your own 15mm eyepieces may help considerably. I know that the interchangeable eyepiece version of the straight through BT100 is capable of quality views. If yours can be modified without excessive cost it seems like it would be a useful thing to do. 25x is nice but some objects look better at higher mags. Having useful higher mag options should make the bins more enjoyable for you.
Rich V
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Binoculars:
33/50/75/150x100 Saturn III, 16x70 FMT-SX, 10x50 PCF-V, 10x43 DCF-SP, 10x35 E2, 7x35 E, 8x30 E2, 7x26 Custom, 8x23AS Diplomat, 8x23 Travelite
Scopes:
C9.25, 6" f8 reflector, SV80S
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Robert A.
sage
Reged: 01/21/05
Posts: 294
Loc: Milwaukee, WI Northern USA
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Idahoman,
Where do you find the eyepiece modification kit for the Oberwerk 25x / 40 100mm Classic? I don't see it for sale at the Oberwerk site. It would be great to change a fixed power giant Oberwerk binoculars to accept most telescope eyepieces, (within reason).
Have I misunderstood you?
Thanks,
Rob
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Oberwerk 11x56, Nikon 12x50se, Fujinon 16x70, William Optics 22x70, Oberwerk 25/40 45degree 100mm
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idahoman
sage
Reged: 11/25/05
Posts: 473
Loc: Idaho, USA
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ITE (reviewed here at Cloudy Nights) had such a setup. But, I think they are no longer in business. If you write Kevin at Oberwerk, he apparently offers such a kit for $300. It is not shown in any of his websites. He told me that it is easily installed by the end user.
Now, wouldn't it be nice if a kit was available that angled the eyepieces 45 degrees?
Rich -- Kevin's response was that the view should be fine at 40x. I notice a poorer view at 40x, particularly when viewing the night sky. I doubt that it is collimation, since I would note problems at 25x as well then. At 25x, these binoculars are absolutely wonderful. I'm wondering if it could be the 40x eyepieces or how they are mounted.
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A Guy In Idaho
43° 31' N 112° 4' W
4780 ft elevation
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14732
Loc: Cumberland, R I , USA42N71.4W
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I recently purchased a used BT100. Now, I'll state up front, I already have a BT100, so I have something to compare too. Well as it turns out, this other used pair were perfectly alligned, even better than mine by a small increment, BUT, they suffered from a considerable amount of astigmatism. Images were very soft.
In fact, the astigmatism was so bad that they could not resolve half as close as mine. Whereas mine could easily resolve 10", and even 6" could be resolved with some effort, this other pair, at the same powers, had trouble with 15", could not separate 10" and could not even tell that 6" was a pair.
If the probelm is astigmatism in the instrument, it is easy to identify. Stars at best focus look like little croses. Racking inward and outward from best focus, you won't see a perfect defocused circle, but you will see a defocused oblong shape and it will flip orientation from in to out.
I have since removed the front retaining rings, and found that the objective lens elements can be rotated in their cell. By rotating the objectives, I have removed a considerable amount of the astigmatism and have removed about half of the error. This rotation process is trial and error, so patience is required. It also requires rechecking collimation, but I'm happy to report that with all the moving of the objectives that I've done, collimation has not changed.
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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idahoman
sage
Reged: 11/25/05
Posts: 473
Loc: Idaho, USA
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Thanks -- I will have to check this out.
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A Guy In Idaho
43° 31' N 112° 4' W
4780 ft elevation
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