[ATM] Re: Second Thoughts on Mirror Support

[brianb at u.washington.edu (B. Bainbridge)]

Many people grind large thin mirrors on a piece of carpet.
Is this use of carpet adequate?


On Wed, 11 Feb 2004, Emery Greg wrote:

> Hi Geoff:
>
> Didn't Dobson originally design his mount to be easy to use as well as to be able to be constructed from common materials by a typical person?
>
> If this is true, the carpet support support is a common material which doesn't require specialized tools or knowledge.  I believe ( on thin ice here) that Dobson's design also had full thickness mirrors which allowed for greater latitude in mirror support/cell design.
>
> ttfn
> greg
>
> ----- Original Message -----
> From: gjnelson@absamail.co.za
> Date: Wednesday, February 11, 2004 7:05 am
> Subject: Re: [ATM] Re: Second Thoughts on Mirror Support
>
> > > The original John Dobson style scopes use carpet, not wiffle
> > trees
> > to
> > > support the mirror.  Thus it does appear to work to some (as yet
> > > unquantified) degree.  Think of  it as a 10000 point variable force
> > > cell.
> >
> >
> > This is a compliant support. Where you have the most force you
> > have
> > the most give thereby increasing the area of support and reducing
> > the
> > point forces. This would give you instead of three points of
> > contact
> > three areas of contact that would essentially merge not each other
> > seamlessly dependent on how flat the support of the carpet is.
> >
> > I guess it could be modelled in PLOP but setting it up or even an
> > approximation of it would be quite a challenge.
> >
> > Now what would happen if you RTV'd the mirror to the carpet? No
> > sling
> > would be required and you will still have a large support area.
> >
> > Geoff
> >
> >
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