Re: [ATM] In-Search-off the "Star Test"

["Bob May" <bobmay@nethere.com>]

Works good and tastes great!
The artificial star is a great device to build buy you have to remember to
put it far enough away from the scope so that the image is in the far field.
Also remember that you're not testing at an infinite distance but rather at
some finite distance so you will have a little bit of spherical aberration
remaining.  There is a formula somewhere that tells you how far you have to
go away to get the SA down to a certain value otherwise you will not be
seeing anything resembling the truth.
Interesting fact - Leon Foucault never did the Foucault test like we do it
but rather did a test for nulling elliptical surfaces.  Final figuring was
by mere inspection of the image for clarity of a far distance item.
Bob May
bobmay@nethere.com
http://nav.to/bobmay
http://bobmay.astronomy.net

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