Hi Gordon,
Pitty you couldn`t get all the data you desired to complete the image but well done on what you have done so far with it.
I hope you don`t mind but I did a bit of selective clipping and a bit of red channel stretching to help with dark noise and to lift the red channel in the crab a little more..just a quick 5 minutes of play in PS.
If you can get another night on it, it shall make alot of difference!..
cheers Gary