basic astrophotography - short exposure/ no rotation synchronisation

basic setup:
nikon d5300 on gorillapod
Lens: 135mm nikkor f/2.8 MF
exposition: 3-5s
sensitivity: iso8000
raw (nikon's fake raw) recording of 50-100 images
moon phase : gibbeuse 60%
flats ~15 and dark ~40
Bias images (1/4000s - dark): ~40
merging progra: Regim (on Linux)
editing levels and noise: Darktable (on Linux)

andromede (centre?)

cassiopee (not totally centred)