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First time using binoviewer, WO. Scope collimation?

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#1 cuivienor

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Posted 12 March 2018 - 10:17 PM

I just got a WO binoviewer, my first ever - I have to same, it is amazing how much more detail I can see with two eyes rather than one! I use it with my 8 inch LX200. I have a problem however, in that while my scope is perfectly collimated with a standard eyepiece, or directly with a camera, it appears to be wildly out of collimation with the binoviewer, with the secondary shadow being very obviously off-center. Is that normal? And anything that can be done about it?

 

Thank you!

 

Yannick



#2 Eddgie

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Posted 13 March 2018 - 08:12 AM

It is not normal, but it happens often.

 

The light path though the binoviewer displaces the focal plane by about 100mm.  This means that any tilt in the system will be more pronounced because the focal plane has moved so far behind the telescope.

 

In Newtonians, this problem will show if the secondary centering is not perfect perfect perfect or  and in refractors it can show if there is any sag in the system(often in the focuser due to the extreme load on standard Crayford pinion shafts) or of the diagonal is out of collimation.

 

In the SCT, most likely is either the diagonal is shifting in the visual back under the weight of the binoviewer, or the diagonal itself is may be out of collimation.

 

At any rate, it s not normal and is most likley something in the front of the Binoviewer, and I would look at the diagonal and mechanical connections first, but an out of center secondary mirror could be a contributor as well.  To test this use a standard eyepiece and see if the secondary shadow shifts orientation as you move the scope though best focus.  If the shadow shifts from one side of the Fresnel Pattern to the other, possible that there is some kind of tilt in the system.



#3 cuivienor

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Posted 13 March 2018 - 09:08 AM

Thank you so much! I'm using an ES dielectric diagonal that is user-collimatable (and I had to collimate it), so it is likely that this is the issue. I will look into collimating that diagonal better (the scope was collimated with camera without diagonal, then I collimated the diagonal using the eyepiece - likely the tilt in the diagonal remains to some extent, and is exacerbated by the binoviewer, as you mentioned)

I will look more into it!

Thank you!

Yannick

#4 Beg

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Posted 14 March 2018 - 01:09 AM

Russ Lederman told me always collimate the scope with the Binoviewer attached. Your diagonal must be way out of whack though, as the WO is pretty light to cause sag. 



#5 cuivienor

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Posted 16 March 2018 - 06:29 AM

Thank you very much! I tested it today on a far away building light (raining), and definitely it was the mirror angle in the diagonal. I was able to adjust it and now, everything works fine!

 

So my conclusion about collimation would be 1) collimate the scope with a camera at prime focus and 2) collimate the diagonal with a binoviewer, to exaggerate any diagonal mirror tilt.


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