binoviewer question

[manu_78]

hi all

just wondering if anyone has experience enough with binoviewers to give me some advice.

just got a great set of binoviewers (i get headaches after looking through my scope with one eye!) and tried them out first up in my dobsonian - and you guessed it, i cant achieve focus. So i did a bit of reading around and although these binoviewers were marketed as being compatible with newtonians, i have read that it has something to do with the focal length etc (i am only very new to astronomy). Anyway, the binoviewers came with a 1.5 barlow which i assume is fine for other scopes. So my question is, if i use a 2x barlow will i be able to achieve focus?

thanks for any help & advice!

[gb_astro]

Manu can you achieve rough focus by pulling the binos out of the focuser tube
a bit (towards you) or do you think they have to be moved further in?

gb.

[Osirisra (Ken)]

What kind of dob have you got? With my dob I have to collapse the tube by a couple on inches to achieve focus.

[casstony]

As Ken says, if it's a collapsible dob you can reduce the length of the scope to get focus.

If it's a solid tube a 2x barlow should work though the effective magnification will be around 4x. (due to the extra lightpath through the binos). When you draw an eyepiece out of a barlow, increasing the separation between the barlow element and the eyepiece, the magnification provided by the barlow increases.

Seibert Optical sells correctors that work at lower magnifications: http://www.siebertoptics.bizland.com/

[wavelandscott (Scott)]

Which kind did you get? Some brands come with an OCS (optical corrector system) that will help you achieve focus.

[dannat (Daniel)]

a 2" barlow still may not let you achieve focus, what brand of binoviewer did you get? a 1.5x OCA is a little unusual

as you are in Melb & i am close by we could meet up -i have a 1.6x william topics OCS you could try -though i am guesing if your focuser has not much travel you need to take a trip to bunnings to buy some longer bolts -place them at the bottom of the mirror cell to lift the mirror cell up the tube -you will need a good 5cm i estimate. most binoviewers add about 10cm to the optical train

pm me if you want to meet up
PS i also get hassles looking thru just one eye for long periods