William Optics Binoviewer and my 10" DOB?

[ken spencer]

Hi all, saw fab review of the William Optics Binoviewer in "sky at night" magazine but cant focus in my 10" Dobsonian. What am I doing wrong?

Thanks

Ken

[red dwalf]

silly question but you are using the focuser on the scope ?

if so, on some scopes a 1.6 barlow is needed to achive focus, should be included with the binos usually, it`s just a very small adapter that fits onto the end of the binos.

[Ad Astra]

Many dobs simply don't have the focal range for a binoviewer to work properly.

I've only ever seen them used on cassegrains and refractors.

Dan

[ken spencer]

Strange, I can get them to focus on near by trees but not beyond? And yes I have used the small adapter that comes with them. Excellent on the 127 MAK but appears to be unusable on my 10" DOB.

Regards

ken

[Johnboy]

Strange, I can get them to focus on near by trees but not beyond? And yes I have used the small adapter that comes with them. Excellent on the 127 MAK but appears to be unusable on my 10" DOB.

Regards

ken

I had the same problem when I had my 12" dob. I found a 2" extension tube fitted to the nose piece of the binoviewer did the trick.

Hope this helps.

John

[kniclander]

it's because with the extra light path thru the binoviewers you dont have enought in travel. adding barlows helps but the distance between the barlow and the e/ps actually inreases the effect of the barlow so you end up with very high mags. there's also an issue that you are effecively stopping down your aperture so turning your 10" into about a 6". I had exactly the same issues and ended up just using the mak for binoviewing whi.ch is absolutely brilliant. If you look on CN there's loads of threads on this (and if you want to understand the stopping down point which I dont:o)

can't see how adding an extension tube would help as that will further increase the length of the light path:icon_scratch:

[Johnboy]

can't see how adding an extension tube would help as that will further increase the length of the light path:icon_scratch:

All I can say it worked for me...

[ken spencer]

Thanks again, Kniclander what magnification do you get with the Binoviewer using the small barlow in the MAK? I know it uses 20mm lens so that should give me 150x that MAK being 1500mm. I was looking at Saturn and it seems a lot more than 150x

Thanks

Ken

[kniclander]

in the mak I dont use the barlow at all - it comes to focus fine without it. if you've got the barlow stuck in the nose end of the binoviewers it's probably operating at about 1.5 times its basic power. there was a thread a while ago where a much cleverer person had actually worked out the efects of putting the barlow in different places. also, using a binoviewer actuallly increases the focal length of the scope too - making a 1500 effectively about an 1700. seriously, if you want to blind yourself witht he science, go to cloudy nights....

enjoy the binoviewing.