On Mon, 06 Oct 2003 10:00:08 -0400, "André P." ...reflected:

Hi all !

Since I have only Newton type télecope, I don't have experience about
refractors.

Do you have a refractor, and will its focusser accept 2" eyepieces
or a 2" diagonal? If so, then you'd almost have to go with a mirroring
diagonal. If not, then it's probably a 1.25" focusser, in which case you
could go with either, a mirror or a prism.

Here my question:

Witch is the best between prism diagonal and miror diagonal and why ?

I personally prefer prisms, while others prefer mirrored diagonals, but
with my preference perhaps the result of inexperience rather than having
tested both.

Give us some more information before we go any further.

Alan