Thanks guys. I was fairly impressed with the sharpness for a single exposure.
It was right in the centre, taking up somewhere between half and two third of the width of the frame. This image is nice and sharp; does that mean the OTA is well collimated, or is it possible it's still not quite spot on? I've got a Cheshire but I'm not 100% sure I've got everything just right - I know an f/5 scope has an offset secondary but not sure how that affects collimation....