bino with gso dob

[doug mc]

Thinking of getting a GSO 10 inch dobsonian. I want to use bino viewer. I have a W.O. unit. I also have a 1.6 x ocs and a 2 x 2 inch GSO Ed barlow. How much extension will I need to reach focus. I assumean extension tube between the barlow and the bino will be needed.

[dannat]

will be best to push the mirror up the tube somewhat, I would think atleast 5cm, otherwise youll have either too much mag. or the b/viewer will be stuck way out. you can use lnger bolts/heavier springs while youre at it -just the same as if you're moddding for photo d-slr to reach focus,

if you put ext between barlow & unit you will multiply the barlow effect, instead of 2x it may turn out to be close to 3x magnificartion

[doug mc]

Moving the mirror is probably the best way, although only enough to reach focus with an ocs or the ED barlow screwed into the 2 inch to 1.25 eyepiece adapter, as an f/5 optic is too fast for my bino. I will have to use an OCS anyhow.