2026-10-09 APP 2.0.0-beta48 has been released !
This is mainly a bug fix release for the reported bugs in beta47. In addition it has a significant User Interface performance improvement noticable when you need to process 1000s of images in APP.
2026-10-03 APP 2.0.0-beta47 has been released !
This is a very big release... many code optimizations/rewrites, many parts of APP are much faster and more precise, especially star analysis and registration are much faster ! Big mosaics will go much faster 🙂
And we introduce a new preview filter, which includes the new Adaptive Deep Sky Stretch and a General Levels Stretch, this has been long over due. The old preview filter (the panel on the right side to stretch and preview your data) has not been updated for a couple of years and it is a critical part of any APP session.
Adaptive Deep Sky Stretch or ADSS is a much more intuitive stretch algorithm. It is also color preserving (which is a great new addition in itself ! ) which means that the highlights are no longer bleached, color is maintained from the linear data while stretching. You can simply stretch your data using the sky background level and signal width sliders which work much easier and more intuitive. You no longer need to fiddle with the old complicated sliders with zoom buttons. All the zoom buttons for the sliders are made redundant. And you can enter slider values in the slider value fields yourself. I will make a youtube video in the coming days to explain and fully introduce ADSS. Once the video is ready, it will be highlighted on the forum.
RGB Combine upgrade !. The RGB Combine Tool has been rewritten mostly. The tool is faster and easier to use and most importantly, the Luminance slider to inject a luminance channel or channels into the RGB composite is now working correctly. It no longer bleaches the RGB colors. Combined with the new ADSS preview, you will get much better and easier great composites with great color! I will also explain this in a new youtube video.
APP is having trouble managing my 9-panel Milky Way panorama. The Analyse Stars step is a bottleneck: APP apparently can't detect usable patterns in the multitude of tiny stars. It'll work if I set the Automatic Star #s Target slider to the max, but the resulting files become so large that to assemble the mosaic APP asks for 3X the amount of RAM that my computer can provide. It'll scale down the result, but the resulting image is unrecognizable. Is there a special workflow for assembling such a mosaic? I'm using 9 panels from a full-frame Canon DSLR, .raw files, 18mm FL lens.
See https://www.astropixelprocessor.com/community/tutorials-workflows/green-panels-wont-respond-to-the-mosaic-workflow for a workflow that will probably do the trick.
What works OK for me in these cases is to stack the individual panels (if you have multiple exposures for them), then combine the stacks into a mosaic. If memory  or disk space is an issue, set the "scale" to something below 1 in the 6) Integrate tab.
Keep an eye on the Registration RMS values after the 4) Register step. These values should ideally be well below 1 pixel. If they're not, something probably went wrong in the registration step, and (very) strange images may result.
@ralphThanks, Ralph. I didn't know about the Scale setting and will give it a try. Can you explain the RMS values? Thanks.
The Register step takes the stars it found in the 3) Analyse Stars step, groups them in patterns, and tries to match the patterns between the panels. Too few stars and there are too few patterns and the match will fail. Depending on the freedom given to the alignment algorithm (dynamic distortion correction, same camera and optics, registration mode) the match between the patterns found may be better or worse. The Root Mean Square difference of the star positions is an indicator of how well the algorithm performed. APP can do very good alignments, with good enough signal to noise in the images I've had values below 0.1 pixel. For noisier images about 0.3 to 0.6 pixel is quite good.
However, I've encountered RMS values in some of my milky way mosaics that seem to take forever to converge, and result in huge stacked images, similar to what you describe. The RMS value seemed acceptable at a value of about 1 or 2 pixels, just a bit on the high side. But the resulting stack had crazy distortion where the smart algorithm had the bad luck of noisy star patterns as input and enough freedom to try and make things match. And the algorithm did find matches, however nothing that was realistic.
it takes a bit of fiddling around with the various settings and workflow to get a decent convergence to the correct mosaic. APP is very good at what it does, but there is no sure fire way that I know of that works for anything.
A couple of things that helped me get good mosaic results:
- try to get high(er) signal to noise ratio in the images to be aligned. Remember that for aligning there is no absolute need to keep the colour information. So if needed I try to stack all exposures for a single panel, irrespective of filter band, into a panel that has very well defined stars. These panels are then used for the alignment.
- When taking the exposures, increase the overlap between the panels. I have not experimented too much and don't know for sure where the sweep spot is. Too little overlap might result in too few star patterns found between overlapping panels and increases the risk for occasional mis-identification of star patterns
- Split the registration step from the integration step for tricky mosaics. That's described in the linked workflow above.
