Re: (ATM) Ferguson's mirror 1

[Mel Bartels <mbartels@efn.org>]

Remember that RFT (Rich Field Telescope) is defined by field of view, so the
focal ratio doesn't matter except when it becomes too extreme for today's
eyepieces.  A f/6 with 35mm to 40mm wide angle eyepiece will have the same
view as a f/4 with 24mm eyepiece. So, don't go for a 8" f/4 unless you have
an overriding issue such as tube length (which I cannot imagine that you
would in this size).  An 8" f/6 will give you a good chance at figuring
properly, plus be able to give you higher magnifications a little easier.

Regards,
Mel Bartels
mailto:mbartels@efn.org
http://www.efn.org/~mbartels