Coma and focal ratio

David Knisely wrote:
However, much of what is seen in shorter focal length instruments is not coma,
but astigmatism caused by the eyepiece being unable to deal with the steeper
light cone. For that, a more complex and better corrected eyepiece is
needed. If coma is still a bother, then an external coma corrrector such as
the Tele Vue Paracorr will take most of it out. I have used one in an 8 inch
f/5, and while I can see a slight improvement in the view, the coma isn't all
that bad without the Paracorr (aberrations at the edges are still dominated
by those caused by the eyepiece).

This brings up a question I'd been meaning to ask. As I've
experimented and observed with different eyepieces, and learned about
what some of these aberrations look like, I've successively upgraded
to better eyepieces. However, even in my f/6 XT8, I see very-slightly
non-sharp stars near the edge in my Pan 35. Not troublesome; not even
really noticeable unless one is actually looking at the edge to try
and see how sharp the stars there are. But I always hear "pinpoint to
the edge of the FOV" about this eyepiece, and it makes me wonder if
others really do see truly pinpoint-sharp stars at the edge, or if
this is more of a relative term, since I agree that the Pan 35 is
miles ahead of anything else I've put in that scope in that focal
range.

So, my question: is that likely coma, or is coma so insignicant in an
f/6 as to not be noticeable? Again, the aberration is slight (I'm not
sure how to explain it more precisely with words).

Thanks,
Chris Nicholl