Re: [ATM] two mirror folded newtonian

["McHatten, Shawn" <Shawn.McHatten@aliant.ca>]

Hey Guys
	Thanks for the suggestions. Just to explain a little further the
donor asked that we build a scope from the mirror and not keep passing
it on. It has already changed hands several times because no one wants
that long a focal length scope. The Center would like to build a "Center
Scope" that we can loan out to members and take to community events.
These events often bring out little people and thus the requirement to
get the observing height down. We can climb some steps but getting a 4
ft eye height up another 4 ft (6 steps) seems too much. So those are our
book ends.
	The requirement to use a diagonal doesn't really bother me too
much. Although not optimal, Catadioptic and refractor owners use them
almost every night they go out. 
	Secondary size does worry me a little but we're hoping we can
keep it below 20% but may have to go to 25%. All my reading says that
going below 15% won't make a noticeable difference. 
	Baffling worries me the most and that is one of the reasons I
posted the question. What have others done with this type of scope to
get around some of these problems? I know there are a few of us that
have done them since I remember reading some of the posts. Just can't
find them in the archives. I must be using the wrong search words. Every
hit I get for "folded Newtonian" brings back the one with a tertiary
mirror design.
	I'd love to see us build a "dual" spider/upper cage design so
that in normal use we would have the lower observing height but for
those of us more experienced that want the extra contrast and don't mind
climbing a ladder we could have a second cage or configurable spider
design. Not too worried about that yet though. We can work on that
later. See we don't even have the thing built yet and I'm already
upgrading :).
	So anyone out there done a Newtonian with secondary at more than
45 degrees. Any hints for looking this up in the archives.

Thanks
Shawn

McHatten, Shawn wrote:
> 	Our Centre has recently acquired a 2in thick 12.5in f8 mirror.
> We are looking at building a truss tube scope out of it but a normal
> Newtonian design will push the Zenith observing height to around 8ft.
A
> little high for our liking. I suggested that we look at the folded
> design that I have seen a couple of you working on. 

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