From: "Dwight K. Elvey" 
To: atm{at}shore.net
Reply-To: "Dwight K. Elvey" 


>From: "Jon Wilson" 
>
>About the Foucalt test. Practice is the best way to master its use.
>
>Personally, I like the Ronchi test. If you've got an known set of
lines/inch (or lines/mm) on the grating, it's more accurate.

?????
Dwight

>
>However, even the Ronchi takes some practice. A good reference for Foucalt
images is the old Amateur Telescope Making books, by Ingles (through
Scientific American).
>
>Good luck:-)
>Jon

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