Restoration of solar images by the Steer algorithm

Restoration of diffuse features and computational time have been more serious problems in solar observations than in non-solar observations because of complicated brightness structures in enormous time-series images. The CLEAN algorithm proposed by Steer et al. was applied to the data processing of the Nobeyama Radioheliograph to solve these problems, and restores daily solar images well in an automatic data processing routine. A single set of parameters used in the algorithm can cover a wide range of solar activity. The algorithm also has the advantage of requiring less computational time and is optimized to require one-tenth the time of the classical Högbom algorithm.