Re: ATM 8" Cass Blank,

[Joe Mayenschein <mayen1@mwt.net>]

Bob May wrote:

> 8"F30 R-C scope for looking at the planets?  Magnification of the secondary
> would be 7.5 and that would also make for a fairly small secondary.
> Needless to say, the 240" focal length would make for a very easy scope to
> use with large longer focal length eyepieces.  It wouldn't be very good tho
> looking at larger objects as the moon would more than fill any 2" EP.

Upon this suggestion from Bob I began some research on the R-C Design,

Hyperbolic Primary (weak)
Hyperbolic secondary  (strong)

Ok,  now,, the question is,,  most of the designs seem to have a fast F
ratio,,  lots faster than a normal cass. Almost in the ranges of a standard
newtonian type of f ratio.

So,,  how would this effect the strengths of this long beast of a f ratio
scope? I would assume a LOT weaker and much closer to a sphere correct?

as far as the secondary size goes,, no matter how small I can make it,, I see
no need to go less than the central hole of 2.6"

Or baffling will really be a nightmare!

What's everyone's thoughts?

Joe

>
> Bob May
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> bobmay@nethere.com
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