The colour of comet ISON

The colour of comet ISON, a photo by Trois_Merlettes on Flickr.

Via Flickr:
Comet C/2012 (ISON) reached magnitude 7.9 this morning and the sky was reasonably clear albeit a little hazy but it became possible to image its colour. 21 images of 120s have been taken using in regular succession clear, red, green and blue filters. The images are locked on the comet so the stars appear moving but it is the comet which moves during the shooting which lasted 41 minutes. The 3 funfamental colours are then combined to give the true colour of the comet. Green dominates the head of the comet whilst its tail becomes progressively reddish as plasma starts forming. The tail keeps growing to enormous proportion and it is only the beginning! Telescope: C11-HD; camera: STXL monochrome cooled at -35°C