Re: [ATM] Pinhole size article in ATM 3

["Olivier Biot" <olivier.biot@gmail.com>]

I don't want to initiate a debate and maybe my post is off-topic, but
I understood you do not require a pinhole for a Foucault test.

A couple fellow ATMers used to make a pinhole in Aluminium flashing
paper. One day the flashing paper fell off and the guy doing the
Foucault test was stunned to see that it worked! This happened a
couple years ago.

The first year after this 'accident' they compared Foucault test
results with and without a pinhole in front of the light source. After
this they never used a pinhole again.

I know I won't use a pinhole for the Foucault test setup I will use at
home in short (once we're polishing with a pitch lap).

Cheers,

Olivier

On 12/11/07, Francis J. O'Reilly <foreilly@verizon.net> wrote:
> Dominic,
>
> I'm sorry that over the last day I misspelled your name.
>
> The article by Burch in ATM 3 concerns the size of the pinhole used in the
> Foucault test.
>
> It is bizzarre in that it is based upon unsupported assumptions, the math is
> off by a factor of ten and in the final computation Burch switches from
> English units to metric without any explanation whatsoever as to how he gets
> there.
>
> It is a short article that I missed for about twenty years, but now reading
> it I can say that it must have been added to the volume by Ingalls for comic
> relief.
>
> Francis
> ----- Original Message -----
> From: "Dominic-Luc Webb" <dlwebb@canit.se>
> To: "Francis J. O'Reilly" <foreilly@verizon.net>
> Sent: Tuesday, December 11, 2007 3:53 AM
> Subject: Re: [ATM] ATM You Tube Group
>
>
> >
> > On Mon, 10 Dec 2007, Francis J. O'Reilly wrote:
> >
> >> If you have a copy of ATM #3, please read the article by Burch on page 65
> >> relating to pinhole size.
> >
> > Off list for the moment....
> >
> > I do not have this article, but if it relates to optical testers, I
> > am just now considering this issue myself. Could you offer a
> > sentence or two what this is?
> >
> > Dominic
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