Grant - Nice image but stacking on comets shouldn't be that hard! Astrometrica is a great tool for this with the benefit that you can get astrometry and photometry at the same time. Astrometrica stacks on the predicted ephemeris offset of the comet so there is no need for manual alignment. 

The fun was that thin cloud was going through and changing transparency fast. Also, it was reflecting Moonlight and causing sky gradients that varied from frame to frame. Plus, it was near the horizon over a sports field - so floodlights.

Median stacking struggled to give an ideal result as the effective gain changes and the global sky count went up and down like  yoyo - messing up the assumption on which it works. Sigma only did slightly better. I can think of ways round this (I think AA8 is doing one of them but not both) which will add nothing in good conditions but may help rescue data like this.

On Astrometrica. I have a licence somewhere ,but the config file I made for using it when using my old Newt+SXV7 never worked and I was never able to establish why.   :)

I used the manual option for the stacking because I was simultaneously checking that AstroArt was rejecting all the images with poor guiding and where satellites went near the comet - apart from Starlinks I was unlucky enough to find 2 other satellites went right over the comet itself. Its probably my most satellite polluted run of all time. Yeah, I should have just platesolved the frames.