Skywatcher OAG - focus issue

[Superdavo]

I recently bought a SkyWatcher off axis guider, and tonight I have tried to use it with my Canon 1100D camera, and SW200P telescope, but I have been having issues with getting it to focus - when I try to focus it, the focuser reaches the scope before it can reach focus - and so won't go any further.

Has anyone else had this issue before? If so, what can I do?

David

[Ruud]

A barlow might help you reach focus.

[Superdavo]

Thanks! Won't that increase the zoom though?

David

[Ruud]

Yes, I can imagine you might not want that.

How do you use the guider? With the Canon?

[Superdavo]

Yeah, with the Canon. It's connected with the supplied 2'' adaptor to the scope.

David

[steppenwolf]

This is a common problem I'm afraid with adding anything to the light path on a Newtonian reflector. Is this a 'Blue Tube' 200P with the R & P focuser? If so, you are likely to struggle resolving this easily.

A Barlow may indeed assist here but the issue then is a doubling of the apparent focal length. The second possible solution is to use a Baader MP Coma Corrector as this not only helps to get rid of coma but it gives you an extra 10mm of backfocus to play with which *may* be enough. The third solution is to fit a low profile focuser.

[Superdavo]

It's a black tube scope. Roughly how much extra backfocus do you think a new focuser would give me? It looked like I was getting fairly close to achieving focus, so 10mm may be enough.

David

[steppenwolf]

My Reflector had the old R & P focuser so I changed it for a Baader Steeltrack which measurest 60mm from the 2" EP holder mounting face to the optical tube wall when fully wound in, if that helps.

[Superdavo]

Thanks! Gonna be goin to bed now, so I'll have to look at it more tomorrow.

David