You could also use the scope with a round secondary mirror (no need for a eliptical secondary!) to reflect the light back to next to the primary and thus you can have a cass looking instrument. That way, you can do a long tube and not have to climb a long ladder to get to the top. The mirror is of such a long FL that you can do it a bit off axis and not get beyond the 1/4wave limit. You can also bring the focus point out at the declination axix (the naysmyth type focus point). There`s so many names for these various designs where you bring out the focus out of the tube and the nicest for a very long FL is to bring it out through the RA axis which makes the EP stationary through the night.