Illustration of the algorithm behind the image trigger for one energy strip. The vertical dotted lines delimit portions of 20.48 s. The green blocks correspond to shadowgrams that are corrected and deconvolved. The blue blocks correspond to the images of the sky. For visibility, only scales n = 0, n = 1, and n = 2 are shown (scale n = 6 is the result of the sum of 64 images of 20.48 s).