A couple of difference processing trials here. Still coming to terms with the ultra red from the modded camera.
17/180sec images @ ISO800, dark subtracted. Modded 20D, ED80, aligned and combined initially in IP. Image 2 is a straight Median combine using IP Digital Development and a touch of colour balance in PS. Image 1 is a layer combine in PS of a number of IP combined images (average, adaptive add, median, with varying amounts of DD) in an attempt to reduce noise, colour and to highlight the comet. Don't know how successful it was.
I'll have another go at processing the unprocessed combines in PS without the Digital Development later. I find the DD introduces too much noise for my liking.