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Equipment Discussions >> Binoviewers
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PowerM3
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Reged: 08/31/10

Vignetting with Denk II 8” LX200 using Reducer Mod new
      #4083235 - 09/30/10 02:19 PM
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Hello, I recently acquired a used set of Denk II’s and absolutely love the views they provide! I’m using them with an 8” LX200 and a GSO 2” SCT dielectric diagonal. I have 3 sets of eyepieces currently 12.4mm Meade Plossels, 20mm Meade QX’s wide fields, and 32mm proOptic Plossels.

All of the eyepiece sets work absolutely wonderful in 2x and 1.15x mode without ANY vignetting, but the 32mm and somewhat the 20mm wide fields seem to have some vignetting and in particular on the right side of the FOV and more so in the left eye in essentially a crescent shape. With the 20mm this is almost an non issue, with the 32mm this is defiantly very noticeable but that eyepiece set seems to have a dark halo around the entire outer edge of the FOV. The 12.4mm plossels do not vignetting at all even in focal reduction mode.

My question is of course: is this is normal? Also I would really appreciate it if someone snapped a few pictures of their Denk II nosepiece side and posted them up. In my set of binos you can clearly see the sharp edge of the front prism and I would like to compare to see if that’s how its supposed to look.
Thanks, and clear skies!

Edited by PowerM3 (09/30/10 02:20 PM)

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EdZ
Professor EdZ
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Re: Vignetting with Denk II 8” LX200 using Reducer Mod new [Re: PowerM3]
      #4083405 - 09/30/10 03:44 PM
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Quote:

In my set of binos you can clearly see the sharp edge of the front prism and I would like to compare to see if that’s how its supposed to look.




You may see this in other denks, but NO, that is not how it is supposed to look.

My Denks showed a thin sliver of exposed prism edge. In all cases, the prism edges should be covered by the round edge of the housing. This will produce a perfectly round exit pupil. If you do have an exposed edge, that thin sliver is void of light and is not contributing to the exit pupil. If you were to project your exit pupil on the wall till it's large enough to see, you could probably see the edge cutoff in the exit pupil.

No, it's not the way it is supposed to be, but Yes, unfortunately, that's the way it is in some Denks.

edz

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PowerM3
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Reged: 08/31/10

Re: Vignetting with Denk II 8” LX200 using Reducer Mod new [Re: EdZ]
      #4084807 - 10/01/10 12:29 AM
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Thanks for the reply EdZ. So do you think that what I'm experiencing is normal in the focal reduction mode?

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RonBurgundy
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Reged: 06/16/09

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Re: Vignetting with Denk II 8” LX200 using Reducer Mod new [Re: PowerM3]
      #4084908 - 10/01/10 01:41 AM
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I don't think this is a normal reaction. No, not at all!

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GlennLeDrew
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Reged: 06/18/08

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Re: Vignetting with Denk II 8” LX200 using Reducer Mod new [Re: RonBurgundy]
      #4085775 - 10/01/10 01:22 PM
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Quote:

With the 20mm this is almost an non issue, with the 32mm this is defiantly very noticeable but that eyepiece set seems to have a dark halo around the entire outer edge of the FOV.



The 32mm ocular has a larger field stop than does the 20mm, which clearly is larger than the rear prism aperture on the BV. So what you're seeing is the out of focus edge of the (smaller) prism aperture, which appears as the fuzzy-edged darkening at the field edge.

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thesubwaypusher
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Reged: 07/08/04

Loc: New York City
Re: Vignetting with Denk II 8” LX200 using Reducer Mod [Re: PowerM3]
      #4087059 - 10/02/10 01:55 AM
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As Glen says, basically, your Denks have a 26mm clear aperture, and the field stops in your troublesome eyepieces are probably 27mm.

Chris

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