ATM Coma and RFT designs

["Phil Marcus" <pmarcus@wt.net>]

I'm making an 8" RFT scope and passersby suggest that f/4.5
is just too deep a curve to go for.  They cite figuring
problems and say "it'll never be better than 1/4 wave".  It
has been suggested that I go for f/5 instead of f/4.5.

Anyone have any suggestions as to whether 4.5 is too short
for good visual, the desirability of going a little longer
or whether this is all just a bunch of nonsense?