If this is non-zero, then a ringing filter is applied to the residuals once the FLT model has been removed. This filter attempts to locate and flag residuals that suffer from ringing. It gives the size of the box used to smooth the residuals in order to determine the background. It is specified as a multiple of the filter size. A value of 0.5 could be a good starting point. Note, the ringing filter is not applied on any initial iterations specified by parameter "ast.skip" . [0]

MAKEMAP, CALCQU