The observed FUV ISRF in Habig units along the minor axis of M 82 are plotted as a function of the distance from the galaxy center in ″, for the south (left) and north (right) outflow separately. The blue symbols connected by the blue line, are the values calculated in the pure geometrical dilution hypothesis. The starburst region, which occupies the central 250 pc (~15″) is not included. (This figure is available in color in the electronic form.)