More attempt.  This time, the brightness/contrast different between panels seem to reduced. I had used the advanced and multiply-scale options for normalization. I am not sure whether this combination of parameters is responsible for the improvement. 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. 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. Cheers, Wei-HaoScreen Shot 2017-05-09 at 10.57.57 PM

Hi Mabula, Thank you.  The new system warning should be very useful.  700 MP is already slightly larger than the largest mosaic that I had ever built: http://www.astrobin.com/250543/?nc=user Is 32bit floating point the internal data format for APP?  Does relaxing it to 16bit floating point allow for 1.4 GP images without significant rebuilt of APP? I finally am able to create a full mosaic using all panels without running into troubles. I used a scale of 0.2 to avoid potential errors. The result is attached. You can see that there are still issues: 1. The Milky Way is not straight. I guess this has something to do with who the reference is. Is it possible to make it straight in some way? None of the panels are perfectly at the middle of the Galactic plane. They are either above or below. So it is not possible to pick a reference frame that makes the projection right at the Galactic plane. 2. There are still brightness/contrast differences between the panels. I used multiply-scale for normalization. I can try if it becomes better if add-scale is used, but I guess not. I also used the advanced normalization. 3. The registration is wrong in many ways. As far as I recall, the various parameter I used are, calibrated projection, equirectangular, and dynamic distortion correction. Anything I can do to improve the registration? Cheers, Wei-HaoScreen Shot 2017-05-08 at 11.24.39 PM

Hi Mabula, I will try with your recommended parameters tomorrow.  Here are a few additional related and unrelated points. 1. I believe I used equirectangularProjection instead of the standard rectlinearProjection.  I might be wrong. 2. I also did try a small subset of the panels to start with.  APP can process them successfully.  Please see the attached image.  Here, my question is whether I can control the orientation of the FOV, to be either horizontal or vertical.  The tilted angle like this doesn't look quite comfortable. 3. I believe what PI did for image stacking is to register every image to the reference frame.  If all of the images are taken with identical optics, then the stacked result can be considered as having no distortion correction at all.  It should have identical distortion pattern of the reference frame. 4. I have another project to mosaic the 2pi sky. Do you think either of the current two projection methods in APP can do that?  When I started the project, I had fisheye projection in mind. 5. It takes couple of minutes for my computer to launch APP. This is more than 10x slower than any other programs I have. Is this normal? Cheers, Wei-HaoScreen Shot 2017-05-07 at 12.47.09 AM