Deciding on proper focal plane location in Newtonians
Hi, y'all. Can anyone tell me the best way to determine where you want to put the focal plane when designing a new scope? I'm planning what I call The Dark Companion Mk II, and it will have an f/4.5 primary. I plan to purchase expensive 2" eyepieces. With a wide real field, I want my focuser as short as I can get it, but I need to know how far from the optical axis to put it. I tried to determine the optimum location by looking up the numbers for Tele-View eyepieces, which seem to have the most complete published specs. Though they give the position of the field stop, I don't see where they give the actual location of the focal plane relative to the shoulder of the eyepiece barrel. Is there any way to derive this from the info they provide? Thanks for any comments.
