Binoviewer focusing problem

[Eric48]

Dear binoviewer users, I'm seeking advice about a focusing problem with my very new WO binoviewers.

I have a GSO 302mm newtonian on dob mount but I can't bring the binoviewers into focus for distant objects like the moon, planets etc - in short, the very things I want to look at. I just can't focus in enough (towards the tube) despite using the x1.6 corrector which came with the WO package.

I understand there is a x2 barlow and an extender that is made by WO to fit the WO binos. Has anyone any info on whether one or other or both would help me focus down enough?

I believe an alternative way to fix the problem would be to fit a low profile focuser but I'm not too keen on that.

Very grateful for any advice.

Eric

[Merlin66]

If the WO are similar to the AE version I have, you need about 110mm of back focus to make them work.
They seem to be easy/ better to use on SCT systems.
A x2 barlow should push the focus out far enough but at the cost of the added magnification & loss of FOV.
I don't think most Bino viewers work (well) with eyepieces greater than 18mm, so using a barlow will unfortunately give effectively a maximum eyepiece fl of 8mm or so.....

[Eric48]

Thanks Merlin. I did try a x2 shorty plus barlow & got focus but with what seemed to be dimmer image compared to the x1.6 that came with the binoviewers when focussed on something close enough to get focus. Was using the 20mm eyepieces which came with the WO package.

Now found an article on internet by Glenn Muller about a solution offered by Siebert optics so might have to give them a go even tho' it might be a shot in the dark.

Thanks,
Eric

[Eric48]

Just a quick update to say that the fix from Siebert Optics using a 1.25x corrector worked a treat on my 302 dob and even left room for more in-focus when focussed on distant object. See one of pix below.

Used the WO binoviewers last night and got very pretty views of Saturn and the jewel box before very heavy condensation defeated me. View thro' the binoviewers seems more solid or more steady perhaps - but might be just a trick of the brain. I'm very happy with end result in any case.