Re: clarification on split-ring mnt. post
Stephen Spangler (sspang@cpcnet.com)
Fri, 5 May 1995 11:32:19 00000
> I am really greatful for the responses I got to my help call. Upon
>reading my message over (I should have done that before I posted), I
>discovered that I left out a few crucial words accidentally, thereby
>turning my question into nonsensical technobabble.
>
> What I was trying to ask is how much larger should the aperture of
>the top cylinder (i.e the one inclosing the diagonal mirror) be than the
>diameter of the 12.25" primary in order to preserve the wide field of view,
>but keep that aperture to a minimum.
>
>I hope this is clearer. I'll also post some of my thoughts on the design
>later today or tomorow. Thanks,
>
> - Dan Feldkhun
>
Dan,
My experience leads me to believe that the tube should be a minimum of 1.5"
larger in diameter than the primary mirror (13.75" for a 12.25" mirror, 14"
for a 12.5"). A good program to check this out is called NEWT. It runs
under Windows and provides a graphical view of the light entering the scope
and shows areas of conflict.
However, the guys in the club are experimenting with the idea that the tube
should be considerable larger than the primary (like 16" id for a 12.5"
mirror) and baffled. I've looked through a scope constructed like that and
it performed well. When I get back my 12.5" mirror from the coaters and put
it in my 14" unbaffled strut tube, we're gonna compare side-by-side and see
what happens.
Steve