How did you process the images? With a OSC you have to debayer first otherwise you'll be stacking different coloured pixels on top of each other and you'll never get the colour right, and it tends to blur the stars. eg:
star in frame 1
RGRG
GBGB
same star in a later frame with a one pixel drift
GRGR
BGBG
Stack before debayer:
R+G R+G
G+B G+B
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