honyi

Having used both CEM and GEM designs (and my personal mount is a CEM40, after upgrading from a CEM25p), I find that the CEM design is great for refractors and SCT/RCs, but unwieldy for newtonians. Especially smaller newtonians. This is because the imaging train will then be comparatively heavier than the primary mirror, and the whole tube has to be pushed backwards in order to balance in declination. However, the length of the imaging train hanging downwards means that there is a strict limit on how far you can push it backwards before it clashes with the CEM's counterweight shaft housing. I have had to use a counterweight at the rear of the tube to help balance the set up in declination. This problem is less pronounced when the newtonian is mounted on a GEM mount, because the whole tube can be pushed backwards quite a bit further and it still will not make contact with the counterweight shaft or mount head.