It's not quite as simple as it looks . Firstly, you have to add adjustable
altitude, or you are limited to using it fairly close to the latitude it was
designed for[ if you want to track using only one axis]. Secondly, you need to make it so the tube rotates easily in it's support block, because
if you don't, the balance is affected as you move around the sky. When the scope is one side of the zenith, the focuser and the eyepiece are
on the side of the tube furthest from the centre line, and when the
scope is the other side of the zenith the focuser and EP are on the side nearest to the centre line. You could eliminate this problem by having the focuser on the "back' of the tube, so the balance is not affected, but the
focuser would be in an incredibly awkward position, and you'd have to sit astride the tube in order to be comfortable.
.This latter problem
wouldn't apply to very small Dobs of course. I built a wedge for my
10"dob thinking that I could come up with an adjustable
counterweight system, managed that, but the eyepiece got into such
awful positions that I gave up on the experiment.
raymo