Certainly triagluar cells would be stiffer, but that doesn't mean that parrallel tubes aren't stiff enough.
We can speculate all we want, but until we measure what's happening, we won't know.
That also brings up the question of what's stiff enough. How stiff does a telescope need to be for visual use, etc.
-------------- Original message --------------
From: "Richard Crisp" <rdcrisp@No-Spam>
> the truss tube designs I have seen on the typical dob aren't structurally
> very rigid from twisting
>
> parallel tubes just have that property
>
> triangles arranged properly are far stiffer
>
> might that be it?
>
>
> ----- Original Message -----
> From: "Michelle Stone"
> To: ; "The Astronomy Connection"
>
> Sent: Thursday, March 13, 2008 7:47 PM
> Subject: Re: offlist Re: [TAC] Collimation question!
>
>
> > How much is it moving Mark? I've noticed in most dobsonian designs
> > that there is a combination of reasons that add up to some flex in
> > collimation. (Yes, even on the scopes that I build). No system will
> > be perfectly rigid. The key is to not let it interfere with the
> > views. So it at least needs to be stiff enough to provide pleasing
> > images for the majority of cases. If you collimate at the 60 degree
> > mark, then you are pretty well covered for most of the observing
> > range. You rarely observe down parallel to the earth... that's where
> > you want it to be the worst.
> >
> > Michelle
> >
> > On Thu, Mar 13, 2008 at 7:43 PM, Mark Wagner
> > wrote:
> >> Richard Crisp wrote:
> >>
> >> > the sling type cell support seems to be hard to guarantee to not move
> >>
> >>
> >> Its not in a sling. The mirror is a conical, center bolted, onto a cell
> >> that has six support
> >> points to the OTA. Its seems very securely mounted.
> >>
> >>
> >> --
> >> GSSP Web Page updated 3/4/08: http://www.goldenstatestarparty.org
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> >>
> > --
> > GSSP Web Page updated 3/4/08: http://www.goldenstatestarparty.org
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>
> --
> GSSP Web Page updated 3/4/08: http://www.goldenstatestarparty.org
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--
GSSP Web Page updated 3/4/08: http://www.goldenstatestarparty.org
Who's observing where? - http://observers.org/OI-calendar/
Mailing list preferences: http://seds.org/mailman/listinfo/sf-bay-tac
Received on Thu Mar 13 20:09:37 2008