Yeh I have imaged a comet before. I thought you had imaged the comet when it wasn't in the cluster and then pasted it in where it was supposed to have been on a particular date. Instead you imaged the comet when it was actually in the cluster and then pasted it into the cluster shot, taken earlier, in a position where it would have been at a single moment in time, this makes for a slightly more valid alignment capture to me, still a little composed but pretty close
Mike