OAG back focus question

[redeye64 (Paul)]

l'm intending to put an OAG on my refractor (svbony 102mm with 0.8 reducer). l currently have a svbony filter drawer (21mm) and cam is a asi533.
ls my only real option the zwo oag, which is 16.5mm and would replace the existing 16.5 spacer?
My preference would be the askar oag which is 19.5mm and has an integrated helical focusser but don't know how to get around that extra 3mm?? l don't want to remove the reducer
Back focus is 55mm btw......

[Drac0 (Mark)]

Hi Paul,

Been thinking about this & really can't see any way you can get the wider OAG to fit in with the filter drawer there.

I guess it's a design issue with these types of cameras where they require the female-female adapter to connect to many accessories. Would probably be better if they made it a female thread on the camera so you could use a male-male adapter if needed which would give an extra few mm to work with in your situation. But it is what it is.

Cheers,
Mark

[Joshua Bunn (Joshua)]

Hello Paul,


I see your issue here with the 2 male m42 threads at the front of the camera. I can offer a potential solution, if the camera side of the filter draw has sufficient depth to accept a male threaded adapter, I can machine out the male m42 thread and replace it with a female m54 for example (or smaller, it doesnt really matter). Then have an adapter from the camera of m42 female to the filter draw of m54 for example, with 3mm of BF. This will get you to 55mm (also need to account for filter thickness).