Re: [ATM] ritchey cretians

["Khail Rosenberg" <mikhail.rosenberg@rosenbergtelescopes.com>]

It seems that the begineers always have better spheres... the people that i
have trained get better looking ones a bit quicker. makes me a bit
jealous... and one thing that technology can not do :) gives me a slight
smile on my face just thinking about that part

On 1/20/08, Lawrence D. Lopez <lopez@mv.mv.com> wrote:
>
> Mitchell:
>
>     It's an observation, not an ambition.
>
>     It has been observed that many mechanical mirror making
>     mechanisms turn out terrible mirrors because they are systematic.
>
>     This doesn't mean that it can't be done or that it hasn't been done.
>
>     By the same token humans systematically grinding mirrors have the
>     same problems.
>
>     It's only by introducing randomness in the right way that
>     you get a perfect surface.
>
>     It isn't magic.
>
>     You are trying to get two surfaces to meet at any orientation.
>     The only surfaces that do that are planes and spheres.
>     Everything else is worn down.
>     To meet the any orientation requirement you need to randomly
>     grind in all orientations.
>
>     This is very very basic mirror making.
>
> Larry
>
>
>
> Mitchell R wrote:
> > Interesting - as a novice to this whole optical fabrication thing,
> > I am not familiar with the details of current practice in design
> > and using of machines for working glass, so I may be talking through
> > my hat here... but why is it your ambition to never use machines to
> > make mirrors? I should think that (in principle at least) it should
> > be possible to make a grinding/polishing machine that would give full
> > control of the profile of the work and better blending of the surface
> > figure than the normal hand methods (even for glass of more modest
> size)...
> >
> >      **Quite the opposite actually. Machines do the exact same motion
> over
> > and over and over and over (I think you get it ;) so small errors are
> > multiplied many times. With hand work no two strokes will ever be
> exactly
> > the same so they blend very nicely if you keep them all reasonably the
> same
> > length/pressure.
> >
> > Mitchell
> >
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> >
> >
>
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