From: klowther{at}cisnet.com
To: dwightk.elvey{at}amd.com, atm{at}shore.net
Reply-To: klowther{at}cisnet.com


I think this method is based on a 'least glass removal' theory and the fact
that we seem to
have a simple process to do it.  Long strokes deepen the center and turn
the edge.  Result, if
you are lucky, is a parabola.

Ken

----- Original Message -----
From: Dwight K. Elvey 
Sent: Wednesday, May 07, 2003 12:43:00 PM To: 
Subject: Re: ATM dumb question, maybe

>
> >From: "Bianco Giuseppe" 
> >
> >Even if I've a PhD in Astronomy and reasonable knowledge in optics, I'm
puzzled
> by something which will be certainly solved by somebody in the list.
> >Textbooks on mirror making say that, in order to
"parabolize" a concave
> spherical mirror, one should dig into the center of the surface;
conversely, in
> order to "hyperbolize" a convex spherical mirror, one should
depress the
outer
> zones of the surface. To me, both those action lead straight to an
ellipsoidal
> figure. In fact, in the case of a concave surface, a paraboloid results
from
> flattening the outer zones with respect to the center, and even more so
in the
> case of an hyperboloid.
> >Where's the trick? Thank you all in advance.
> >
> >Dr. Giuseppe Bianco
> >Centro di Geodesia Spaziale "G. Colombo"
> >Agenzia Spaziale Italiana
> >75100 Matera (MT), Italy
> >phone:+39-0835-377209
> >fax:     +39-0835-339005
> >e-mail: giuseppe.bianco{at}asi.it
> >
>
> Hi
>  You need to think of these shapes as a continuum of shapes.
> An ellipsoid is just a stretched shpere. A paraboliod is a
> particular one that has been stretched to infinity. The
> hyperboloid is a continuation to the stretching.
>  To modify a sphere to any of these shapes, we can progress
> the same way. The suggestions for where to remove the most
> material can be used to change the shape from a sphere to
> ellipsoids, to a paraboloid and then to hyperboloids. It
> is more a case of how much, not where. The where is the
> same for all of them.
> Dwight
>
>
>
>

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