Collimating a newtonian with a filter wheel attached

[John K]

This will sound like a silly question but when attaching a filter wheel to a newtonian focuser should the collimation procedure occur with or without the filter wheel attached to the focuser?

With my set up the filter wheel is attached to the focuser, then a 5 x powermate and then my Skynyx.

So far I have been collimating before attaching the filter wheel. But have also tried it after attaching the filter wheel and there is a slight difference.

Which method would produce the best results and why?

[Tandum]

There shouldn't be a difference in collimation with and without a filter wheel. I'd suggest your focuser tube is sagging with the weight of the wheel attached.

[John K]

I actually think it's the 1 1/4" adaptor that I have on my 2" filter wheel might be the issue as it only goes in half way - but when it's on the focuser it sits flush.