Rotating Stars

[steppenwolf]

I think that potentially not de-Bayering the images is having an affect here as the Bayer matrix will be present as a grid that will rotate as the images are stacked thus perhaps giving this smearing effect.

Is the image of the Rosette above de-Bayered and then converted to mono or has it not been de-Bayered in the first place?

Have you applied Bias and Dark calibration? If not, this too would contribute noise and add to the smearing effect when the images were stacked.

[happy-kat]

I'm not looking at the smearing noise as such but that the star shapes on the right hand side are considerably more elongated than on the left, I get this on one of my lenses particularly.

I had expected a fairly equal star distortion on both sides of the image posted but it's much stronger on the right and the image is the same orientation as it was taken. I'm not sure this can be put down totally to field rotation. Hence the suggestion of much shorter exposure test.