Re: ATM 4 tubes truss structure questions...

[Ken Hunter <atm_ken_hunter@yahoo.com>]

--- Benoit Schillings <benoit@be.com> wrote:
> Ken, I'm curious.
> 
> Why would it be a terrible design for an imaging
> instrument ?
> 
The book I mentioned goes into detail the design and
compromises made for this class of instrument. The
secondary is a VERY large percentage of the primary
area and the supporting structure diffraction is an
added MINUS for imaging. There is another design you
might be interested in. It is being exploited by
Robert Romeo and the Carbon Fiber boys in Tucson that
uses a central tube of graphite composition with the
secondary mounted on 4 small graphite vanes at the end
of the central tube.

I'll try acsii art:

                __________
               |secondary |
              _|__________|_
              \ \        / /
               \ \______/ / <--- vanes
                \|      |/
                 |      |
                 | tube |

> Are you refrering to the diffraction effects of the
> tubes ?
> 
> 
 Yes! The above ascii drawing shows an idea that is
more in line with an imaging system.

> I use a concentric Schmidt cassegrain with spider
> 3/8 thick, this doesn't seem to impact much on the
image.
> 
>
The scope in the URL you posted has very thick spider
vanes and supports which enable it to slew (very
quickly) without much vibration of the secondary.
 
> Thank you for the help !
> 
> 
>               -- Benoit
> 

You're welcome!

Ken Hunter
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