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I think Zaps is right in that most people put one in there because they see them on other commercial designs, and they would be embarrassed to pony up and say "I put it on there because I didn't know any better".
So far everyone seems to be in agreement that it would be silly to add one to a pier unless there was no other option.
However, many piers have them, so are they compromising the mount?
Now I hear about people 'ring testing' the mount by hitting it on the side with a hammer.
Brendan points out that we rarely do this while imaging, but that doesn't mean it is a totally pointless exercise (though it may be). We often test things in extreme ways to find out their potential strengths and weaknesses.
So what does the hammer test tell us?
I know if I walk near my EQ6 on tripod that I get vibrations that affect the image, I can quantify that quite easily.
Has anyone tried imaging with and without a top-plate and gotten a different result? Or has anyone managed to induce vibration in one with a top-plate that has been fixed by removing it?
Or has someone got the math that would show some potential problem with the top-plate.
Again, I think they are a stupid idea (though I could be wrong), but I'd like to know how much they affect things, and under what circumstances?
(I had similar questions long ago about vixen vs losmandy bars, everyone told me losmandy was better and stronger, many people spent good money upgrading, but amazingly I couldn't find a single piece of empirical evidence of its superiority in use).
So do the rat-cages screw things up or not? If you have a 3m long scope and windy conditions, could it make a difference?
Brendan, you have said that they don't if you know what you are doing, can you elaborate on what knowing what you're doing entails from a design standpoint?
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