From: "McHatten, Shawn" 
To: ATM shore 
Reply-To: "McHatten, Shawn" 


Hey Gang
        Simple question. If I have a small 4in spherical mirror say f15 (60in
focal length), how far off axis can I place the eyepiece (ie no secondary)
before I run into problems.
        Just thinking about the Mersenne design and if one could replace the
tertiary (Nasmyth I think) flat with a spherical mirror and push the focus
back up the tube out to the side. With a 16in primary this would push the
eyepiece 8in (more like 10in) off axis. Even worse the larger you go.  You
loose the ability to bring the image out through the alt axis but you don't
need the "second" scope (usually a refractor). The tertiary
becomes the second scope. Just thinking out loud. Any ideas?

Thanks
Shawn

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