Fig. 2
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Grading system for the considered α sunspot is based on its stability during its transit, and whether or not it has companions, and how it evolves. The highest grade of 3 is given to exemplary α spots that are visible for an entire crossing of the solar disk, which are isolated without other features nearby, and which stay in a mostly constant shape. The examples for each sunspot-grade category were created by overlaying images from each time series.
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