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Actually Dave, there are most likely a variety of errors at play in these shots. Guiding is evident in 2 shots (either poor guide parameters or differential flexure), focusor slop is another error in at least one other shot (that is the most likely cause of the elongation on one side).
If the mirrors were not well figured you would see blurry detail on the targets, these images look pretty sharp.
A flattener will only flattener the elongated stars that radiate from the centre of the image near the edge of the field. If the camera is not square to the optical line it will produce elongation on side of the image or at worst it can cause elongation on one side and out of focus stars on the other. That is what I have on my eta image. Yet when 4945 was shot it was directly over head and the camera was hanging almost vertical. Its all a matter of reasoning it out.
Thanks for the links and your thoughts.
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