Hi Everyone,
Thanks for the responses, I will have a play with JPEG and TIF's (at a smaller size) and see if I can see any differences.
Attached is the image I took as a test and I have circled the parts that go a bit weird.
For the Camera speed I suspect the timer setting was too long between frames (I had 5 seconds after looking at it again), the SD card in the camera is one of the fastest I could buy at the time so I don't think this was the problem
But thanks for the idea as it always helps to rule these things out.
Anyway, red circles aside this was my first star trails from my backyard.
Cheers
Anthony