[blink138 (Pat)]

Originally Posted by sheeny

Alistair, have a look at this:

http://www.iceinspace.com.au/forum/s...ht=collimation

Is it any help to you? (As Mark has pointed out, I should've called them Fresnel discs not Airy discs!)

Al.

ha ha... nice one centurion.......... i like it!
pat