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Mike, Your astigmatism could well be caused by the bonding of your secondary. I think `bonding' mirrors in any photographic scope is quite probelematic. You don't want the optics to shift around as the scope tracks across the sky but at the same time if the silastic bond is too thin it will stress the mirrors as it cures. In my experience diagonals need to have at least a 3mm thick silicone blobs or twisting can occur.
I think mechanical edge clips are really the only sound way to go for this purpose. The first Meade 16" Lightbridge I looked through up at Kulnura had obvious astigmatism at high power but where do you start the diagnosis when both mirrors are stuck down with silicon ?
Is it possible to rotate the primary mirror by actaully spinning the whole cell until the mounting holes line up , to see if the astigmatic orientation changes.
Mark
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