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Binoviewer problem

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#1 banjaxed

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Posted 21 January 2020 - 05:02 AM

I have recently purchased an Astro Engineering bino viewer and a pair of 15mm Plossl eyepieces. I found a copy of the original instructions which were very clear and it looked like an easy task to get set up and focused. I used my 127 mak as it is not supposed to need a barlow or extension to obtain focus but all I am getting is a white light through the lenses however much I adjust the eyepiece focus or the telescope focus. Does anyone have any idea why this is happening or could the binoviewer be faulty ? Any help would be greatly appreciated.



#2 junomike

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Posted 21 January 2020 - 07:24 AM

It's possible but highly unlikely the BV's are faulty.

Adding BV's pushes the focal point further back and requires the mirror to be moved further forward.

Try starting  with the focus knob at the end of focus range (stop)  and cycle through slowly until you see an image.

Might take a few tries.



#3 banjaxed

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Posted 21 January 2020 - 08:02 AM

It's possible but highly unlikely the BV's are faulty.

Adding BV's pushes the focal point further back and requires the mirror to be moved further forward.

Try starting  with the focus knob at the end of focus range (stop)  and cycle through slowly until you see an image.

Might take a few tries.

Thank you, I will give your suggestion a try and maybe use a Barlow to see if it makes any difference.



#4 TOMDEY

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Posted 21 January 2020 - 08:16 AM

Binoviewers are like Star Diagonals in that they require substantial differential back-focus from your scope. If you cascade the Star Diagonal and the Binoviewer together... that can add more than your scope allows. And, even if you can achieve focus... your scope is then being used far from its nominal PM-SM spacing, introducing spherical aberration and vignetting... which may be tolerable, but not ideal. Many binoviewers comprise an optional integral Barlow (aka negative relay), to push the image back (eg Binotron Powerswitch), and one uses a positive relay to add no net image shift requirement (TS-Optics/Orion). Binoviewers have a lot going for them, but also involve a lot of performance tradeoffs/compromises.    Tom

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  • 16 Orion Linear binoviewer.jpg


#5 Shorty Barlow

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Posted 21 January 2020 - 08:28 AM

It's possible that you just haven't turned the focuser back far enough yet. I have a Sky-Watcher 127mm Mak and a William Optics binoviewer.

 

med_gallery_249298_10580_328481.jpg

 

Over the years I have tried a variety of eyepiece pairs, including 10mm SvBony aspherics, 12mm GSO Plossls, 15mm TV Plossls, 17mm Barsta Plossls and 18mm BCO's. 

 

I have three nosepiece Barlows: 1.6x, 2x and 2.6x. I could achieve focus with them all. You may have to experiment with the focus travel a bit though.



#6 banjaxed

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Posted 21 January 2020 - 12:59 PM

thank you for your suggestions, I will try again tomorrow as it is very wet and miserable here tonight.



#7 banjaxed

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Posted 22 January 2020 - 12:51 PM

I have discovered that if I use a diagonal 

focus can be achieved but can’t really understand why. I would love to use the binos with my Dob but cannot get focus at all even tried the diagonal without success.


Edited by banjaxed, 22 January 2020 - 12:52 PM.


#8 junomike

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Posted 22 January 2020 - 08:38 PM

You will need an OCS (usually 1.6X or 2.0X) in order to reach focus with a Dob/Newt as the Focal Point is fixed so the OCS moves it were Focus can be reached.



#9 banjaxed

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Posted 23 January 2020 - 05:43 AM

You will need an OCS (usually 1.6X or 2.0X) in order to reach focus with a Dob/Newt as the Focal Point is fixed so the OCS moves it were Focus can be reached.

Thanks for the info, I will give it a try.




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