This chapter documents CASA's refactored imager. These features are visible to the user via the tclean task.

The first five sections give an algorithm-centric view of the imager framework and are meant to convey the overall iterative reconstruction framework and how various algorithms and usage options fit into it. The other sections are more user-centric and focus on what one would need to know about specific imaging goals such as wideband imaging, mosaicking or details about spectral-cube definitions, etc. There is some overlap in content between sections, but this is meant to address the needs of readers who want to understand how the system works as well as those who want to learn how to approach their specific use case.

NOTE: The older clean task also supports most of the options described here, with a similar internal structure. However, going forward, we will focus on tclean only and mention the older code only in the few instances where it contains functionality that has not yet migrated over.