I'm no expert; but I thought that the general rule of thumb was that
the maximum useful magnification of a given telescope was 50x per inch
of aperture. Given that the newt/dob's you are looking at are 10inch
"theoretically" you should be good for 500x.

I have a 10" f/5 Guan Sheng dob, and personally I hardly really ever
exceed 300x with mine (for planets I mainly use a 9mm plossl with 2x
barlow giving 277x). Anything more than that either gives average
images, or with the eye pieces I have are too annoying to use (FOV/eye
relief).

And as a side note (again I'm no expert); I wouldn't get too hooked up
with the claimed maximum magnification of the scopes, and be looking at
things like accessories, mirror quality differences (if any?) and..
price.

I'm sure theres corrections to be made by the others. I hope that helps
some what.

Clarky wrote:
I was just looking at the dobsonians again, and had another question.

Both the Celestron 10 inch and the Orion 10 inch both say that they
have a "maximum useful magnification" of 600. The Hardin 10 inch
Dob's "maximum useful magnification" is only 250. I know that
magnification isn't all that important, but that seems like a pretty
big jump, although I'm not sure 'cause I'm new to all this. Does
anyone have any thoughts on why the Hardin would be so much lower
than
the other two?