Re: ATM Autres follies de Foucault (More Foucault Follies)

[lindberg <lindberg@olywa.net>]

Roger Ceragioli wrote:

> If you plug my above numbers into TEX, you get an overall rating of about
> 1/3 wave UNDERCORRECTED: the zonal graph DESCENDS from zone 1 to zone 5.
> Same for ADMIR.  Yet, the star test shows definitively that the spherical
> correction is close to perfect.  And after past figuring spells, when I got
> the "correct" readings from the knife edge test that produced beautiful
> wave numbers from TEX and ADMIR, the star test showed my little mirror to
> be about 1/4 wave OVERCORRECTED.  

Roger: 
        If I understand your post, and correct me if I'm wrong here, you are
using the outer radius of the windows of the Couder mask as little "r"
in your knife edge calculations. You should be using as "r" the
measurement to the *middle* of the zone. That is what you are judging
while testing, the average light intensity in the middle of the zone.
You can't judge much of anything at either the inner or outer edges of a
zonal window because of diffraction, as I'm sure you will agree. Run
your numbers again using a revised little "r". I'll bet this brings the
Foucault data and star test data into better agreement.


> What I'm writing here isn't meant to attack the knife edge test, which I in
> fact really LOVE.  

Me too.
        Best regards, Steve.