Re: [ATM] Cassegrain Secondary Magnification

["Bob May" <rmay@nethere.com>]

There's a Cass design calculator on the web, sorry but I don't
have the URL but it is easy to find, that you can explore the
various designs with.  For a planetary scope, the field curvature
can be significant but not overly so as you are only interested
in near on-ais imaging.  You may want o consider something more
than a short F15 scope for doing planetary work if that is all
you are really interested in.  The longer the focal length, the
larger the image and thus the easier it is to see with larger
focal length eyepieces which means that the eye relief is better.
My 200" refractor, even with its simple lens produces excellent
images of Mercury with the cusps of the sunlit part of the planet
being bvery sharp, especially when compared to other scopes of
much shorter focal length.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net


_______________________________________________
ATM mailing list http://www.atmlist.net/