After the last post I had two occasions to image with the same setup.
On the first occasion the sensor looked clean with no hint of artifacts or icing.
On the second occasion there was a small smear that looked like icing in the lower left corner.
For some reason, a vertical line appears only in the frames taken with Halpha filter. The frames taken with clear filter do not show such defects.
I have no idea what that could be. In any case, the sensor of the Apogee camera seems clean.
Takashi

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