Bo. No issues stacking. The stars are elongated in each corner - lens distortion. I'm sure someone more knowledgeable can tell you the type of distortion.
Stopping the lens down or using an external aperture mask in front of the objective, should improve things and give a flatter field. Otherwise, with bias dark and flat frames, the central portion is very nice.
Last edited by rcheshire; 10-07-2017 at 05:40 PM.
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