I'm finishing up polishing a 10.5" F/6 mirror and figured it was time to get to work on my UTA of a truss scope. I already ordered a 1.8 antares secondary thinking it would fit the bill but now I'm not so sure. Here is what I've got so far after drawing up the light cones of both a 1.8 and 2.0 secondary in autocad.
http://i46.tinypic.com/3008dmo.gif
Are you supposed to have the light come to a focus and then expand into the eyepiece as I have it with the 24mm eyepiece?