UPDATE FROM MABULA
I have had a very rough 2 months unfortunately health wise. I was struck 3x in a row with bacterial infections. The second infection occurred  after a routine hospital checkup and I became very sick. I had to rest and take a lot of antibiotics. Once I was recovering and restarting work 1 month ago, I again became sick. The infection was not yet gone, so even more antibiotics and rest was needed. Needless to say, it took a lot of my energy and I needed a lot of rest.
Finally, the infection is really gone and my energy is coming back step-by-step now and I have started work again. I am terribly sorry to have kept you waiting for support. I will address all outstanding questions and e-mails step-by step and will be on the forum daily from today.
APP 2.0.0-beta47 will come soon as well, a lot of work was already completed before I became very ill, so the release is also nearly ready for you. Beta47 will be much faster actually. Many workflows will be more than 2x faster, mosaics can even be 10x faster than before because registration really received a major boost... all compared to beta46. Â Before I release it, I will make sure that everything is working properly and then I will release it.
I've taken two nights of 180-degree fisheye images, one night with H alpha filter, the other with O III. The pointing was adjusted each hour, and 60 exposures of 1 minute each were made, while tracking on the fixed pointing.
The 60 exposures with the same pointing stack nicely, but I can't manage to register the stacks with the different pointing. Distortion is of course extreme with a fisheye lens, which is probably where the problem lies.
Any tips on how to tackle this?
Mmm, tricky one, I've not seen fisheye stacking yet here. What does APP say exactly when you try to stack those? Or what does it look like? I can imagine that the distortion that changes with different pointing might make it very difficult to align them.
It either can't register at all, no matching star pairs found, or gives a bad registration value, typically several tens of pixels RMS, with areas that register OK-ish and other areas that are clearly way off.
The image above is a lucky one where both colours happened to be close enough in pointing to give nice registration. Some others I tried look pretty bad if they register at all.
I tried various amounts of stars, pattern recognitions, distortion correction, and registration model. I haven't played around yet with distortion margin.
I was hoping that the Calibrated Projective registration model would be able to deal with the distortion but that didn't work (yet). It probably needs to know more about the distortion in the lens, whether it's F * tan(theta) or F * theta projection or something else. The lens I used is https://www.sigmaphoto.com/8mm-f35-ex-dg-circular-fisheye
If needed I can upload some of the stacks.
Let me ask Mabula first if it's even a possibility. I might then ask for the data, always interesting if we can implement something that might work with it.
I asked Mabula and this is indeed not really possible. Especially as the view changes, making the distortion very different.
OK, thanks for checking. I'll put my hopes on the "not really possible" as opposed to "not possible" and hope for a (more distant) future update. 😉
That's always a good thing, having a positive mindset. haha The problem with fisheye lenses is that distortion, it's very variable and is likely not possible because it would need to distort the image to be able to align them. It wouldn't look good. Keeping the same point direction might still kind of work like you already noticed.
