Thanks for the suggestions Greg. There is nothing in the optical train between the camera and the focuser, but I like the idea of out of square, I'll have a close look at that tonight. Even with no tracking stars should be round at 1/60th sec @ 1000mmm f/l. I can't imagine why anything
should be suddenly out of square as the only fitting is the T-ring to the focuser, but it appears to be the only logical reason for stars to be elongated with such short exposures.
raymo
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