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binos for dobs

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#1 Howard73

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Posted 18 March 2019 - 05:41 PM

Is a bino acceptable on a Dob? I've read both ways (as in not recommended for reflectors etc)



#2 GShaffer

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Posted 18 March 2019 - 05:49 PM

Rarely use ANY scope 6" or larger for visual without binoviewers anymore......I cant recall the last time I used my 20" dob without them.


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#3 Mike Lynch

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Posted 18 March 2019 - 05:52 PM

My general experience with binoviewers on my old Coulter 10.1" Dob has been quite positive. Each Dob and each pair of eyepieces are likely to work a bit differently together.

 

An OCS will be needed on a 'standard' reflector not built for binoviewers, because you likely can't rack the focuser in far enough to compensate for the extra distance the eyepieces stand back from the focus point.

 

I recall one evening some years ago when I first looked at the Andromeda Galaxy with low power with my binos and Dob, and it was a "WOW!!" moment for me and the others who looked through the binos and Dob combination.

 

As they say, depending on your scope and eyepieces, YMMV!!



#4 Mike Lynch

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Posted 18 March 2019 - 05:54 PM

Rarely use ANY scope 6" or larger for visual without binoviewers anymore......I cant recall the last time I used my 20" dob without them.

I was writing my reply when you sent yours! You encapsulated it very nicely....I just need to get the binos out and USE them more often these days...but the weather has been awful in Central Kentucky...



#5 Eddgie

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Posted 18 March 2019 - 08:24 PM

Is a bino acceptable on a Dob? I've read both ways (as in not recommended for reflectors etc)

Binoviewers work with pretty much every kind of scope but there are a lot of compromises.

 

With Dobs, the compromise is that you have to be willing to accept a minimum of 1.3x increase on focal length to get them to reach focus, and often more than this is required. To make matters worse, you are now also limited to 1.25" eyepieces with their correspondingly small field stops.

 

If you are willing to modify your dob and it is not faster than maybe f/4.5 or so, you can get it to reach focus without some kind of OCS by cutting about 125mm off of the truss poles and upping the size of the secondary mirror. 

 

My own recommendation for dobs and non-binoviewer friendly refractors is to use power switch system like the Denks or Earthwin systems.   These will generally give the lowest power and the widest field, and offer the benefit of having three built in and useful magnifications.


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#6 slavicek

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Posted 20 March 2019 - 08:20 PM

Of course you can use them on Dob. I use them for all but the faintest stuff, where I try to minimize the amount of "glass" light has to go thru.




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