I think some subjects have already discussed this but maybe not for heavy instruments. I currently have a mount that has a useful load of 65kg and on which is mounted a newton weighing about 30kg.
I want to add a parallel refractor with a weight of around 15kg. I've already done the test by putting it on and as the mount is in direct drive I'm having problems balancing it in DEC. This is also where I realized that with the imaging train on the newton it's no longer totally symmetrical and the center of gravity is slightly off-center in relation to its axis. What's more, since the scope is so far from the mount, I have to go up to the maximum counterweight load (60 kg) to balance it in AR.
So I'm wondering whether it wouldn't be better to position them side by side by machining a plate and installing two dovetails on it. Of course, the plate would have to be stiff to avoid excessive bending under the weight of the instruments. The disadvantage I've noticed is that the center of gravity of the whole assembly is inevitably more difficult to adjust so that it's perfectly centered on the DEC axis.
Here's what I've got so far:
- over-and-under :
advantage: weight well centered on the DEC axis
disadvantage: very large counterweight to balance in RA. As a result, the counterweight bar may bend, as the largest counterweights are at the end of the bar. As the bar has a diameter of 60mm and is screwed in M54, I think this is negligible.
- side by side :
advantage: weight of the assembly much closer to the mount and therefore easier RA balancing with fewer counterweights
disadvantage: bending of the support plate for both instruments and more precise DEC balancing to position the assembly's center of gravity on the DEC axis.
Perhaps some of you have already experienced this situation and tested both cases... In any case, I'd be delighted to hear from you.
Thanks in advance.