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A good first start
Did your image stacking include derotation ?
Some packages do this automatically and some dont.
Otherwise I think the elongation is more likely to be lens distortion, field curvature.
Its more radial than anything else.
Even focus might have some contribution depending on your lens.
Stopping down the lens might help with this problem but reduces light on the faint non point source light objects.
However 4 secs without an equatorial mount will give you approx 4x15 arc secs = 60 arc secs of field rotation
The SCP is just off to the bottom left of the image which if field rotation was the problem should mean all stars would be progressively more elongated about the SCP the further to the top right of the image you get - yet the elongation is predominantly at the periphery of the image in all directions
Acrux and Mimosa in the centre are generally round.
Your image scale is probably around 18 arc secs per pixel so without doing the horrible maths for being so close to the pole, any field rotation elongation cannot be greater than 60 arc secs or 4 pixels, and is probably unlikely to be more than a few pixels given your proximity to the pole.
Maybe try to improve the colour using some white balance processing and or curves adjustment.
But its all one step at a time - before you've completed all the steps you'll probably find a year or so has passed ! It just takes time and practice.
Keep it up.
Rally
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