Cherokee wrote:

Since I have a 24mm Konig and an Ultima Barlow, this gives me a 24mm
eyepiece and a 12mm eyepiece, right? Per my other post, it appears I
would next get a 4.8mm eyepiece for 100x????


You certainly could (or something close to it), but a 9.6-mm you
could use with the Barlow for 100X would also give you the option of
50X when used alone, giving you in all a choice of 20X, 40X, 50X, &
100X. There wouldn't be any point to using a 4.8-mm EP with the
Barlow, because at 200X you'd be 'overdriving' your aperture.

OTOH with some 'scope-EP combinations a Barlow can create
difficulties in focusing: if a given EP requires the focuser to be
racked nearly all the way in, with a Barlow it'll likely 'bottom out'
before the view gets sharp. Since your current EP works with your
Barlow, if you can find a(n approximately) 9.6mm that's parfocal with
the 24mm you can be sure it'll be similarly compatible.

--
Odysseus