[ATM] Foucault blind to astigmatism?

[vladimir.galogaza at zg.tel.hr (Vladimir Galogaza)]

Jim,

Even if it is true that:

>It is true that whole-mirror KE (let's not call it Foucault) can see
>primary astigmatism (PA) if its axis isn't lined up with the knife edge
>(see the image on top of http://home.earthlink.net/~burrjaw/atm, an 8"f/6
>mirror with 100 nm of PA at 45?).

BUT! I have never seen an actual shadowgram that will come close
in  sharpnes or details to the simulated  ones like those from Diffract.
Therefore the whole PA  via Foucault talk seems to be only of
academic importance ( in my opinion) because necesary details
of the images are usually lost.
What do you think? Is your experience with actual shadows different?

Regards
Vladimir.


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