Good stuff Al! First, you need to stack on the comet head, not the star. Your spectrum as posted is smeared, and at an angle. The AVI has gif dithering and is not really that useful. I'd have a go if you could get original frames to me (send a pm if you don't still have my email address). In the meantime I screen captured several frames from the AVI and produced the attached. We can do better!!
Cheers -