Re: [ATM] Cassegrain Secondary Magnification

["Alfredo Rainho Neves" <arainho@snowsoft.biz>]

Hi Bob,

I also have an 7.5" F12 achromat that I made, that gives good images on the
planets, but  I had to fold it to make it usable, and I do not have a
motorized mount for it what makes observing a hassle. My Idea is a short
tube all spherical Klevzov-Cassegrain, that would have a long focal length
for planetary work. The problem is I have no data on this design. I tries
playing around with Oslo but my design skill are limited. 

Do you have a photo of your 200" Refractor, it would be interresting to see
it's construction.

Regards,

Alfredo

-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf Of
Bob May
Sent: Sunday, February 24, 2008 11:58 AM
To: atm@atmlist.net
Subject: Re: [ATM] Cassegrain Secondary Magnification

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


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