Another dull fl question for discussion

Hi Group...

Your discussions on various topics really helps me. I live in a very remote
area and don't have access to groups or classes though I do read a lot.

OK, I've posted before about seeking a "dream" Dob. It seems to me (from
reading) that really sharp images come from slightly longer focal
lengths---speaking of Dobs here. Meaning, an f/4 18" Dob is going to reach
deep but isn't going to be a great "star splitter" or planetary obervation
telescope. An f/5 is, perhaps a bit sharper and more forgiving with regards
to collimation. F/6 or f/7 is going to give superior views but is going to
require a ladder...or a second story building!

My desired topic is this. Is there a diminishing return on aperture? For
example, an 18" f/4 would reach deep and wouldn't require pinpoint sharpness
because the faint fuzzies need light gathering more than anything else. But
seeing impacts the big aperture more than it does smaller aperture. So
perhaps, a 14" f/6 or f/7 would actually be more versatile? As I read books
about the people who have made discoveries---visually---seems they gravitate
to longer fl ratios. And it seems the faster setups are primaily made for
convenience of average consumers.

I think, 12-14" Dob with FL of 6 6.5 or 7 might be in an observational sweet
spot.

Could we just discuss it?

Doink