Re: ATM f ratio

[Anthony Stillman <atmer@flash.net>]

>...I was inquiring about, ... your use of the word "useful".

Ron,

I agree, useful field diameter is almost entirely subjective.  Which is one
of the resoans I don't like to put a number on.  But in general what ever
criteria you chose, you will see the same effect.  Namely, for a
parabaloid,  regardless of your selection of f/ratio you can find a slower,
albeit larger system which has more, by the same criteria, useful angular
field.

Anthony