Dumbbell Nebula (untracked) - first attempt

[MessierMatt]

I’m slowly working my way through the brightest DSO’s when the skies allow and focused in on M27 on Friday. Despite the 98% moon and some patchy high cloud I was really happy to be able to view and shoot this target for the first time. I am still learning the best settings for DSS and Rawtherapee so would really appreciate any feedback.

I took 750 lights and stacked the best 80% leading to 608 images, I shot at 25600iso (I am finding I need to use a higher iso to pull enough data when using this untracked set up). I used two different exposure lengths at 0.6s and 0.8s which I can see has left some trailing. 
I stacked using Mosaic mode but unsure if I should be doing this.

I then processed in RawTherapee.

Equipment used; Canon 800D, Skywatcher Explorer 150p, EQ3 mount.

Thanks for reading.