I thought you might like to see how I quickly centre my rotary table.
I found a expanding clamp, the type used to fix pulleys to shafts, that conveniently fits the MT3 hole in my rotab and fits the 10mm end of my little edge detector.
I can pop the clamp in to the hole in the rotab, lower the edge detector in to the clamp, nip it up finger tight, then by either sighting or feeling the two parts of the edge detector , I can align the centre to about 1 thou" or so.