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Alistair
I love the title of this thread - all those problems sound way to familiar. In reality you probably have a combination of those issue.
You're taking the right approach blinking the images and thinking of ways to first identify the problem before trying to fix it. Here is a brain dumpage:
For field rotation:
- I would say try align master to polar align. I'm a recent convert.
- select a guide star in the center of the image if possible.
For differential flex between guider and camera:
- review all mechanics, including primary mirror movement and movement in the focuser on the guide scope
- reduce weight wherever possible
- look into OAG or dual chip camera (both probably not possible)
For 'coma'
- review collimation again, you can borrow my catseye stuff if you want
- improve focus
- try tweaking the primary while imaging to see if you can find the sweet spot.
- try rotating the camera 90 or 180 degrees (sensor might not be square)
James
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