Atik 314L + ED80 SW 0.8 reducer and spacing advice needed

[pixueto]

I am thinking about purchasing an  Aitk 314L +  but since my experience has only been with DSLR astrophotography,  I need some advice on the spacing. I understand the spacing needs to be 55mm, but at which points do I measure it? Also, I have a 2" H alpha filter that goes before the flattener. Will this change the spacing required? I want to use the camera with a SW ED80 and the SW 0.8 reducer.

 

Finally, how do I go about attaching the 314L to canon DSLR lenses (I have the canon F2.8  200mm lens that  would like to use with the ccd if possible -also with a nifty fifty)?

 

Would I need a flattener if I use the camera with a SW200P? 

 

Thank you for your help.

[Tinker1947]

If you're going to use a Reflector you will  be wanting a Coma Corrector, can't be much help with the rest of your queries....