I don't think your collimation is out at all. It looks to me like the light has been cut off by a building or something, the straight line is at the bottom of the image in real terms, Jupiter is getting lower at the moment, your focused image will still be fine even though there was a slight obstruction to the light path.
Did you try the scope on something closer to the Meridian and get the same effect ?
EDIT: That is based on your scope mentioned in your signature, 3 reflective surfaces put South to the top of what you see in the eyepiece.
Cheers
Last edited by JohnG; 28-10-2007 at 12:48 PM.
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