χ² map with the fit departures and arrivals for the model. The color represent the χ² for every pair of chromatic parameters and d_env. The white dots are the starting pair for image reconstructions. The red points represent the found parameters for the final image. The fit always ends in the χ² minimum but far from the correct values ( and d_env = 1). The black solid lines link the start and the final values of one reconstruction.