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.
One reason to take N frames of a subject, rather than one long exposure is that during stacking it is easier to get rid of anomalous things like airplane trails.
With N frames, simple averaging would drop the intensity of an anomaly by 1/N. That is nice, but outlier detection in the stacking algorithm - like kappa-sigma or others can improve on that.
But it obviously takes some number of frames for this to be effective. In the extreme case of N=2, the outlier detection can't really work very well. Even if it did pick the right frame to throw away, you would be throwing away half of your exposure.
My question is what is the minimum value of N where the stacking N frames with outlier detection in APP do a good job? Â
My guess is that it is on the order of N=10, but I am not sure.
The cost of N becoming large is read noise, but many modern CMOS cameras have very low read noise - so low that sky background dominates it in many cases.  Â
About 25-30 frames, give or take, for the best rejection. Less will still work, more works better, but about that amount is the minimum for an optimal correction.
ok, thanks!
