Simulated images integrated between t = 0−45 s and t = 130−175 s (to simulate the long exposures of the UV-375 nm images) for two different source functions. In the left panels a) and b) the production rate is kept constant during the whole simulation, on the right (c) and d)) the production was stopped at t = 5 s. In this case the moving dust cloud has detached from the source at t = 130−175 s and a rather flat brightness distribution can be seen.