Rolling annulus with N = 100 over the processed frame of Fig. 1. Top: examples of the first rolling one (in red), the ninth rolling one (in blue) and the eighteenth rolling one (in green) displayed over the central pixel pavement in the image. Bottom: a complete set of rolling annuli shown in a straight line that represents the distance from the star. The three rolling annuli shown in the top figure are displayed with the same colours.