Thank you for your quick reply. I made my horizon roughly 1° bigger than it actually is. So for long focus length no problem. But I use focal length down to 180mm (sometime 50mm, but thats rare), so I have with my QHY268C 7.5° x 5° FOV. So I would have to cut off nearly 4°, for 1500mm FL I would need only 0.5° (+ offset due to disturbed air and so on near the "horizon")

It would be on the wish list to have this feature: start of capturing depending on focal length :-)

But doesnt matter you guys do all a very good job :-)