Extension tube

[Anthonyexmouth]

Ok, my new scope arrived today, transfered my 294 over and now find myself short of some extension tubes to allow me to put my 290mc onto my ed80.

plan is to use my now relegated ed80 for guiding and lunar while my new stellarmira triplet is my DSO scope.

I want to get a filter drawer for the SM90 soon. 

at present I have the 10mm camera tube with the 20 and 16.5 extensions

whats my cheapest option to now get the 55mm back focus needed for my 290 with the reducer on my ED80?

or do i take the plunge and get the filter drawer now with the needed tubes and just swap the zwo tubes on the 294 over to the 290?

[bruno]

If you bought this new, it should come with all the spacers to achieve 55mm backfocus, it also comes with a little manual showing different setups if not it can be found on the ZWO website.

Just measure from the sensor to the focuser, if you're using a filter the body is counted as a spacer but i think you have to add 1mm for the filter lens?

There is a diagram somewhere showing if backfocus has been achieved

I hope this helpful in some way, & others will come along with further/ better info

Bruno