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Old 10-01-2019, 12:29 AM
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Ukastronomer (Jeremy)
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Am I the only one with Binoviewer problems

Am I the only one with Binoviewer problems

I really wish I could get my William Optic bino viewers to work with my 72mm ED Skywatcher scope


I am now convinced that neither IT nor the 120mm will work with a 2" diagonal and binoviewers
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Old 10-01-2019, 08:33 AM
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Atmos (Colin)
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You are pretty much right there, binoviewers and refractors don’t mix well with 2” diagonals.
Even with a 1.25” diagonal and short threaded components you are likely to need a Glass Path Compensator (GPC) which is a small threaded barlow to increase the back focus to allow a refractor to come into focus.

With my 4” refractor I used a 1.7x GPC which allows another 35mm of back focus from memory, a 1.25” diagonal with all threaded connections.

Both diagonals and binoviewers consume a lot of back focus.
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Old 10-01-2019, 10:40 AM
Saturnine (Jeff)
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Hi Jeremy
When you purchased your W.O. Binoviewers there should have been a pair of 20mm Widefield eyepieces and an 1.6X Optical Corrector in the box. At least mine did and you need to use the OC to reach focus with most refractors. This arrangement increases the magnification of the eyepieces by 1.6X , so that the 20mm then acts like an 12.5mm focal length giving 33.6 X in the 72mm x 420mm Skywatcher and an 2 deg. FOV.
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Old 10-01-2019, 08:54 PM
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Ukastronomer (Jeremy)
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Quote:
Originally Posted by Atmos View Post
You are pretty much right there, binoviewers and refractors don’t mix well with 2” diagonals.
Even with a 1.25” diagonal and short threaded components you are likely to need a Glass Path Compensator (GPC) which is a small threaded barlow to increase the back focus to allow a refractor to come into focus.

With my 4” refractor I used a 1.7x GPC which allows another 35mm of back focus from memory, a 1.25” diagonal with all threaded connections.

Both diagonals and binoviewers consume a lot of back focus.


Thanks so I am not alone, 1.25 does work but 2" is useless, thanks all
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Old 12-01-2019, 02:34 AM
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Ukastronomer (Jeremy)
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I was going to buy a 1.25" diagonal, as I really only have decent 2" ones and they won't blasted well work with the binoviewers.

Then I remembered I had a "Skywatcher" flip mirror I have never used, works a treat and substantial enough, better than a 1.25 diagonal in fact
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