Several later algorithms have tried to correct deficiencies of `CLEAN'.
Steer, Dewdney & Ito (1984) developed a variant of the Clark algorithm in which the minor cycle is replaced by simply taking all points above a sidelobe-dependent threshold, scaling them and then subtracting normally in the major cycle. This saves time compared to `CLEAN', but the radio astronomy community has little experience with this variant of the algorithm. The algorithm's ability to handle different practical situations is therefore somewhat uncertain. It was implemented in classic AIPS as 'SDCLN'.
Segalovitz & Frieden (1978) proposed an ad hoc modification of the dirty beam to enhance the smoothness of the resulting `CLEAN' image. Cornwell (1983) justified a similar prescription as forcing the minimization of the image power (i.e., the sum of the squares of the pixel values) and thus pushing down the extrapolated visibility function. Both approaches seem to ameliorate the striping instability to which `CLEAN' is susceptible.
1996 November 4