Photos of dark sky whose stars appears (photons)
Digital devices
These devices capture the image through the lens in the form of photons that more or less fill the well of each photosite according to the amount of light emitted or reflected by the subject.
These photons generate electrons.
The electrons will then be transferred for their treatment,
One can always distinguish two main stages of treatment to apply to a raw image (which has just been acquired): preprocessing and treatment by itself.
Any raw image contains undesirable effects, inherent to the technology of the system used.
The role of pretreatment is to "clean" the raw image of these effects to extract the value that represents the luminous intensity actually fallen on the pixel.
Image processing applies effectively only to pretreated images 1 & 2
To eliminate the effects, it is necessary to subtract from the raw image an approximation of the additive bias and to divide the result by an image compensating the multiplicative bias.
Recall that noise is a random fluctuation of the signal around its mean value.
The processing of images in amateur astronomy.
Pretreatment of images of the night: it is necessary to synthesize calibration images as noisy as possible.
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