User:Tubas/PlanetarySystemStacker

PlanetarySystemStacker (PSS) is a free astronomy program under GNU General Public License for amateur astronomy image optimisation taken from Moon, Sun and planets like Mars, Jupiter or Saturn.





The program enhances photographs using anvanced shift-and-add methods. It takes many images from observation series and computes an optimized image.

Features and operation
From videos in formats like SER, AVI or MP4 PSS extracts frames. The frames may be collections of photographs taken in formats like TIFF, PNG or FITS as well. Artifacts may pretend a good image sharpness and selected image sequences can also be evaluated manually.

The memory management of the program handles image sequences of many GBytes in size, much bigger than the available computer memory.

The stacking process reduces the image noise by averaging the frames. Atmospheric disturbances not only change the image sharpness but also distort the geometry of the frames. Before averaging they must be non-linearly rectified.



The program automatically orders the frames by sharpness in decreasing order (see image). Individual frames may be manually excluded from further processing if required.

During the image stabilization step the program shifts all frames in respect to the sharpest frame. Because of the different distortion of the frames, this cannot be done perfectly.

Since all frames are more or less distorted, none of them serve as an absolute reference for alignment. Therefore a (selectable) percentage of the sharpest frames is averaged as a reference. Since the distortions are statistical in nature, the result is somewhat blurred but undistorted.

The crucial step is to determine the distortions of all frames compared to the reference. The program covers the image with up to several thousand alignment points and determines the local shifts. In a small square area around each anchor point the displacement is corrected. These patches are combined into an overall image by smooth superposition.

Optionally, post-processing follows the stacking. The program aligns the RGB-channels against each other with subpixel accuracy, automatically or manually. Image details can be worked out with a hierarchy of sharpening filters like unsharp masking, Gaussian filters or bilateral filters and their superposition.

Software


The software is developed in Python and GUI toolkit Qt. The source code and documentation, including the algorithms , are available on Github. Under Python environment PSS can be installed with pip. For installation on Windows systems without Python, an installer is available on Github.

The first stable version was published to public in 2020.

History
Amateur astronomer Rolf Hempel] developed the [[MoonPanoramaMaker (MPM) program to perfect his lunar images. To improve the tiling of the panorama image, he developed PlanetarySystemStacker as a free alternative to other proprietary programs. The currently most popular proprietary stacking program AutoStakkert!3 does not offer post-processing. Many users still resort to the proprietary program Registax for this purpose, which has not been further developed for ten years.