Activity thresholds (Table 3) determined by the spectral ratio plots and assigned to RGB channels. In the images, black indicates the regions excluded because of high geometric angles, while red denotes the low signal regions like shadows and the sky. The shadows, where we still receive decent signals, are shown in shades of blue. Regions where we see activity are in light blue and light pink. Using such images, we can detect the active regions. Image details can be found with corresponding image ID in Table 2.