Focus issues with williams binoviewer in 120ed

[avtaram]

I have a problem bringing the williams optics binoviewer into focus with the evostar 120ed.

Has anyone got a solution to this problem

Avtar

[brantuk]

Are you using the 1.6x Barlow? Try with and without or try a different power barlow. If it's extra "back focus" you need then a focus tube extender might be needed - if it's "inward focus" distance you're after then the only way might be to shorten the ota (cut it down) and I'm guessing you don't want to do that. Hth

[damnut]

Hi Avtar,

Had a similar issue with my less posh short tube 120. It was very sensitive to any lengthening of the optical path, even a short extension (12mm) to use a spare sct diagonal was too much. And there was not enough back travel.

Brantuk has it to rights, I wouldn't shorten the OTA either. Must be another solution somewhere??.

[Stu]

What sort of diagonal are you using? Using a 1.25" saves a fair amount of distance. I got some T2 adaptors and a diagonal with short optical lengths to help reach focus.

Stu

[avtaram]

Hi all,

Thanks for your suggestions.

I emailed Siebert optics about the problem and they recommend thier 1.25x corrector will solve the focusing issue.

It works with a 1.25 diagonal and costs 149 dollars.

I will order one sometime next month.

( strange there is no dollar sign on the keyboard of my ipad , not even on the US English keyboard)

[avtaram]

I forgot to mention I will have get a 1.25 diagonal as well.

Any suggestions ?

[John]

I've been trying just the same thing. Even with a 1.25" diagonal and the 1.6x barlow nosepiece I could not get the WO binoviewers to reach focus with my ED120. I was sort of expecting this though and I got the binoviewers for use with my 12" Orion Optics dob which has a low profile focuser.

A different barlow (more powerful) lens might work or shortening the tube but the latter certainly does not appeal to me. I might try the former though.

[paulastro]

A friend of mine has a 120ED Equinox. It works fine with a SW binoviewer with the supplied barlow and a 2 inch diagonal.

[John]

A friend of mine has a 120ED Equinox. It works fine with a SW binoviewer with the supplied barlow and a 2 inch diagonal.

Thats interesting. With a 2" diagonal my pair comes nowhere near focusing in my ED120. My scope has a Moonlite focuser which is slightly lower profile than the stock one too. I guess the Equinox must have a shorter tube than the ED120 Pro.

[avtaram]

Update on the focusing issue.

The 1.25 Williams diagonal that I ordered from flo arrived yesterday and tonight we had clear skies for about half an hour

so I popped out into the garden to see if the williams binoviewer would come to focus.

I had read on the cloudy nights board the somebody had similar focusing issues and had used a 1.25 diagonal with the

barlow placed in between the focuser and the diagonal, I did likewise.

The only thing showing at about 22:30 was arcturus so I pointed the scope and started to focus.

Arcturus came into sharp focus with about 3 cm still to spare on inward focus.

The clouds then rolled in and I could not try different combinations with and without the barlow.

Very pleased with the result. I won't need the siebert optics corrector after all.

Avtar

[glowjet]

Just in case you did not know, putting the barlow between focuser and diagonal will give you an increase in power of 50%. Good result anyway

[avtaram]

Thanks John,

I did read somewhere that putting the barlow between the focuser and the diagonal gives more magnification but I did not

get the chance to try other combinations.

Still waiting for a clear sky. Raining here in west bromwich at the moment.

Cheers Avtar

[John]

I tried the Baader 2.25x Q-Turret barlow in place of the supplied 1.6x barlow nosepiece and the binoviewers came to focus with my ED120 even with the 2" diagonal in place. Still some inwards focus travel left as well.

[avtaram]

Hello John,

I will try the 2.25 barlow with the 2" diagonal when we get some clear skies.

Avtar