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paul mc c

Binoviewers in a dob.

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Has any one used binoviewers in a dob and if so is there any mod that need done to the scope and are they recomended.

I would be using them in a 12'' f5.3 scope.

Thanks Paul.

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ive read a few thread from people who have/do use them but quite a few seemed to have focusing problems and either had to fit a spacer or remove one to get it to work properly.do a search and im sure there will be a few threads or someone will be along in good time with their experiences

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Yes i have read that many dobs dont have enough back focus,and a barlow helps with this,but im not sure if any barlow can be used,and i have read that some have to move thier primary.

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most if not all OOUK scopes require the use of a 50mm extension tube. assuming this is the case and it can be removed, I'd suspect you could use the binoviewers with no issues?

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I think with the Williams bino's the barlow is an optional extra,but i dont know if any barlow can be used.

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I'd have thought so as with most 2x barlows you can unscrew the elements and screw them on the eyepiece to give 1.6x. 

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I'd have thought so as with most 2x barlows you can unscrew the elements and screw them on the eyepiece to give 1.6x. 

I never knew that.. but that makes sence,thats something new i have learnt today.

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In a thread about a month ago, someone had discovered that there are extra holes on the truss rods of the latest SW 300p flextube Dobs. These seem to be for shortening the secondary to primary mirror distance by 110mm which exactly compensates for the needed back-focus of some typical binoviewers.

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In a thread about a month ago, someone had discovered that there are extra holes on the truss rods of the latest SW 300p flextube Dobs. These seem to be for shortening the secondary to primary mirror distance by 110mm which exactly compensates for the needed back-focus of some typical binoviewers.

Yes i read that on CN forum,SW will probably bring out thier own binoviewers now.

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In a thread about a month ago, someone had discovered that there are extra holes on the truss rods of the latest SW 300p flextube Dobs. These seem to be for shortening the secondary to primary mirror distance by 110mm which exactly compensates for the needed back-focus of some typical binoviewers.

Now that is a good idea. From what I've read, though, the secondary will vignette the light cone if the primary is, in effect, moved closer.

Some people replace the secondary with a smaller one to overcome this. I've no practical experience of this however.

But when properly set up, I think a 300 Dob is one of the best bino platforms, re aperture/FOV/ergonomics etc.

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Now that is a good idea. From what I've read, though, the secondary will vignette the light cone if the primary is, in effect, moved closer.

Some people replace the secondary with a smaller one to overcome this. I've no practical experience of this however.

But when properly set up, I think a 300 Dob is one of the best bino platforms, re aperture/FOV/ergonomics etc.

it would need to be a larger secondary, not smaller. I doubt the benefits would be worth it though and your existing secondary might be just big enough if as most are, it is slightly oversized.

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it would need to be a larger secondary, not smaller. I doubt the benefits would be worth it though and your existing secondary might be just big enough if as most are, it is slightly oversized.

Thanks for the correction, Moonshane, [i was thinking that was the case as I wrote it].........it probably doesn't make a huge difference but I read that on CN where some of the Bino nuts work at mm's of tolerance :-)

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Has any one used binoviewers in a dob and if so is there any mod that need done to the scope and are they recomended.

I would be using them in a 12'' f5.3 scope.

Thanks Paul.

I have used a bino viewer with my OO scope, you do need to remove the spacer. My revelation bino viewer does not need a barlow to focus. Although my scope is f 6 I left OO to fit an appropriate sized secondary and standard focal position when ordering the scope. So I would think your OO scope should work OK without any mod's :smiley:   

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