Well the weather has been so lousy here lately that all I have to look
at with my Orion 80ED is an artificial star. The problem is that it is
only about 20 feet away. I know that this introduces spherical
aberration but I'm uncertain weather it is undercorrection or
overcorrection that is introduced. Does anyone out there actually know
how much SA is introduced with an 80mm f/7.5 scope at that distance?
Thanks