def getsatstars(self, verbose = None):
        """
        Returns the mask of saturated stars after finding them if not yet done.
        Intended mainly for external use.
        """
        if verbose == None:
            verbose = self.verbose
        if not self.satlevel > 0:
            raise RuntimeError, "Cannot determine satstars : you gave satlevel <= 0 !" 
        if self.satstars == None:
            self.findsatstars(verbose = verbose)
        return self.satstars