This year I finally managed to hook up my cameras to my Swaro (heavy 85MM HD) spotting scope and take some still photos and also some videos. I have the full package from Swaro that includes a digiscoping adapter for most lens diameters. It's fairly stable and secure, with everything being held together with threaded connections.
With my large DSLR the total package is quite long and pretty dang heavy. The el cheapo made overseas ball head I'm using (supposed to support the weight) creeps and won't lock as securely as it should. All of this is mounted on a Manfrotto carbon tripod that's rated to something like 15# as I recall. The tripod is steady enough (I think) when I load it down with a rock bag, so I don't think it's the root of the instability problem.
In an attempt to try and cure the problem I put a Really Right Stuff Arca-type clamp on top of the ball head and am mounting the spotting scope on an extension plate in an effort to balance the total package on top of the ball head. That helped a lot but it's still a bit wobbly for my taste. Now, if I lock the mirror up I can get some pretty clear and crisp photos even when I crank the Swaro eyepiece up toward 60X. But I have to hold my mouth just right and still end up deleting about half of the shots because they aren't crisp or sharp enough.
I'm cringing at the thought of having to do this, but the RRS BH-55 looks like an excellent ball head. Does anybody have any experience with this ballhead?