Re: [ATM] Phase Contrast and Foucault image puzzle

[Ric Rokosz <radicell2@yahoo.com>]

--- Dale Eason <atmpob@yahoo.com> wrote:

> 
> The fouculat image presents a puzzle to me.  It has
> a
> very strange surface.  This mirror was made by a
> local
> ATM 60 years ago and it has been in storage or on a
> shelf ever since.  I think he was 17 when he made it
> and made and used a machine to make it.  It is
> uncoated Pyrex 10 inch F5.  It has been cored part
> way
> through.  The surface looks very smooth with no hint
> of what is seen here except for 2 small scratches
> and
> the finger prints close to the edge.

Like Mel said,heavy pressure on the lap - a very hard
lap - can cause this.Also before polishing pads came
on the scene there was a technique used (in the time
frame that mirror was made-60 odd years ago) where the
material from a plastic shower curtain or window shade
was placed on the tool and used as a "quick" polish
material.Not the best idea but atm's then,like now,
tried various approaches to cut polishing times.

If you have a copy of ATM Book 2 look on page 24 and
there is a Foc-gram of a mirror with similar surface
features.Seems to have been typical of that era.

Also if you read pages 366 in ATM book 1 some people
used waxes -even floor wax on the pitch to help things
along - too much hard wax and the effect was opposite
to what you wonted.

Ric

Ric

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