Imaging Comets

[grantboxer]

Hi All,
I have imaged a couple of comets and in both instances I have either had to track on the comet or do a comet align when stacking frames. In both cases you get smeared stars, because the comet is moving relative to the star field. How do the "experts" get a nice image of the comet with pin-point stars? Do they "cheat" and superimpose the background star field on the comet image?
Regards Grant

[alocky]

I'm no expert, but here's one I did of Lemmon last year. You create two sets of aligned images - pixinsight is really good at this. One set you align on the comet nucleus, and the other on the background stars. When you stack the two sets you use a very strict rejection tolerance and produce two images - one of the comet, and one of the background stars. Then if you've used the same sub as the reference for both processes you can just add the two images together.
http://www.astrobin.com/32255/C/
hope it helps,
Cheers,
Andrew.

[grantboxer]

Thanks Andrew,

thought there might be some trick to it! I also use PixInsight.

cheers Grant

[cometcatcher]

http://deepskystacker.free.fr/english/userguide.htm#imagepreview

There's an option in deep sky stacker to stack on the comet and also have pin point stars. I haven't used it this way myself, I personally don't mind trailed stars.