Re: [ATM] Re: [atm_free] The zonal Foucault test is freeofinherent correction bias - some supporting graphs

[Ken Lowther <hermit@outofoptions.org>]

Quoting Guy Brandenburg <gfbrandenburg@yahoo.com>:

> I am currently browsing a newly-acquired copy of John
> Strong's book on laboratory physical techniques
> (formerly out of print but available from Lindsay
> Books as a reprint). He points out that Foucault tests
> are sensitive to parallax, and has a method of working
> around that by using a half-silvered mirror so that
> the examiner's eye and the ray of light coming out
> towards the mirror are in exactly the same spot.
> I know that I always have about an inch or two of
> parallax when I use a Couder mask.
>

I know that I, and at least one other, have noticed trying to do video 
of faster mirrors for testing that this is a problem.

Ken

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