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Welcome to the OpenSkyStacker wiki!
OpenSkyStacker assists in the processing of deep-sky images. Stacking in this context means taking the average of several exposures of the same object to reduce the noise and boost the signal-to-noise ratio. This is especially helpful in the field of astrophotography because many objects of interest are so dim that, without processing, they might be indistinguishable from noise.
OpenSkyStacker is not unique in what it accomplishes, as there is other stacking software out there, but it is unique in that it is free, open-source, and available for nearly any operating system.
The software can be downloaded for Windows, Mac, and Ubuntu from the releases page. Users on other Linux distros can build from source.
Noise is the enemy of astrophotography. Some details might be so faint that there are only a few photons hitting the sensor every second. Stacking and calibration reduces the noise to bring out those details. The final image is a 32-bit floating point image, allowing for even the smallest values to be usable for processing.
Below is a crop of M42, the Orion Nebula. One frame is a single exposure; the other was generated by OpenSkyStacker using 32 light frames, 15 dark frames, 25 dark flat frames, and 25 flat frames. The same processing has been applied to both.
Note that the field has been flattened, the background noise has been dramatically reduced, and you can see a lot more gas and dust that would otherwise have been lost in the noise.