Hi @whwang,
Thank you again for your feedback.
“On the other hand, the registration is still terribly wrong. I increased the detected stars to more than 6000. Typical registration rms is between 1 and 3 and number of stars is less than half of the detected stars. For registration, I used dynamic distortion correction and calibrated projective, and no same camera and optics.”
Yes, I am going to work on the (calibrated) projective mosaic algorithms. I know that especially the calibrated version needs a big upgrade to work well (with your data). I have delayed improving the algorithms until a dataset comes along that can clearly show the limits of the current algorithm. I think your data is calling for an upgrade, so I’ll work on it and I will let you know when you can test it ;-)
The amount of stars that is used in registration depends on the amount of overlap between the frame and it’s reference. So if 2000 stars are registered out of a possible 6000 that are detected in the frames, this would roughly mean that the frame and it’s reference overlap for 2000/6000 = 1/3 or 33%. And I have artificial intelligence (Bayesian inference) in place to expand the initial registration hypothesis to the extreme corners of the area for which the two frames have overlap.
“One thing I might do is to to pick one unstacked raw frame for each panel and feed them to APP. This way, there should be absolutely no additional distortion introduced by the stacking in PixInsight. (I still do not believe PixInsight had introduced any distortion, but it wouldn’t hurt to test and verify this.) Unfortunately this will have to wait for a couple of weeks.”
I haven’t seen your data so I can’t say a lot about any distortion introduced by PI, I only know from experience and testing myself with distortion correction in PI, that it can be a problem. Like I said before, if your panels were integrated without PI’s distortion correction, then we shouldn’t worry about this. And you could get a better result with “same camera and optics” on. If only homographies were used by PI, then the distortion pattern of your data shouldn’t be changed like you indicated as well.
The main problem currently is that the calibrated mosaic algorithm doens’t model the center of distortion yet for the panels. This really needs to be improved to get better results.
I would be very interested to see what happens, if you register only single untouched subs of the panels. The best way to create your mosaic, I think, is to make a distortion model using only individual subs of all 40 panels. Then save this model, and use this model in the creation of the panels. Then the mosaic integration should turn out much better. This is the way I used in for instance the 9 panel of Yves of the Nan to Crescent.
“Unfortunately this will have to wait for a couple of weeks.”
I would advise to wait with further testing until I have had time to improve the algortihms so no problem at all ;-)