Some changes from what has been posted before
1) Format Explorer - DSLR_RAW - double-click
Select Create Raw Bayer CFA_Image (note the monochrome key word!) + no black point correction
2) Open your image
3) Process | ColorSpaces | Debayer
RGGB & apply to your opened image
4) Use the ScreenTransferFunction to see what's up in the image. Just press the boxed A on the left
Your image is teal tinted.
5) Use BackgroundModelization | AutomaticBackgroundExtractor
Use the defaults but, under Target Image Correction, select Subtraction (or Division, I did not see a difference but someone like Vicent will know better which one is better!) - Apply. Voila.
6) While the image is more "watchable", it looks noisy. But I do not know how long was the exposure and the likes. It has not been calibrated, and without stacking a few... well, there is that random signal/noise thing.
7) Someone more adept can now tell me how to make this better.
Cheers,