Re: [ATM] 10" sonotube vs. truss

[Ross Sackett <rsackett00@yahoo.com>]

--- Mike Shuken <mikeshuken@value.net> wrote:
>,,, I will be using a 10" f/5
> mirror.  I know that I can 
> build it using a sonotube, but would it be worth the
> effort to build a 
> truss design instead?

Mike,

I think you have correctly anticipated the tradeoffs
here.  The sonotube 10" will be heavy--my 10" f/5 OTA
came in at 70 lbs., even with a thin tube.  But the
truss is much more work to build, and can be
frustrating if not made with precision (so yes, plan
to put in more time).

If you decide to go with the truss, remember that in
general the smaller the aperture the higher the center
of gravity.  If you are building an Obsession-class
truss dob, you will need to make the mirror box deeper
than on a bigger dob.  You might also find, however,
that at the smaller aperture the weight difference
between sonotube and truss aren't significantly
different.

For an alternative truss design that works well at
this aperture see Barry Leger's article in S&T
(December 2000) or Google his name to find a number of
scopes based on it made by others (I used to have the
URL of a pdf of his article, but I can't find it). 
Barry's design looks like an easy build and can be
marvelously compact.

Ross






	
		
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