Chapter 5
Making Images from Interferometer Data

This chapter is devoted to the use of  to make and improve images from interferometer visibility data. It begins with a brief description of the routes by which such data arrive in . The basics of weighting, gridding, and Fourier transforming the data to make the so-called “dirty” image are described, followed by a discussion of deconvolution, particularly Clean. The output of Clean is a model of the sky which, in cases of good signal-to-noise, can be fed back to improve the calibration of the interferometer data, a process called “self-calibration.” How this is done in  is described. This entire process often isolates bad data samples, not previously removed from the data set. An interactive, baseline-based data editor called EDITR is described at the end of the chapter. You may find it more useful than TVFLG (�O.1.6) for removing data at this stage in the processing. Task IMAGR now does “3-dimensional” imaging, SCMAP contains an editing option at each self-calibration cycle, and EDITR has replaced IBLED as the baseline-based editor of choice. A UV -plane based interactive editor called UFLAG is now available.

Lists of  software appropriate to this chapter can be obtained at your terminal by typing ABOUT UV  C R, ABOUT CALIBRATION  C R, ABOUT EDITING  C R, and ABOUT IMAGING  C R. Relatively recent versions of these lists are also given in Chapter 13 below. Basic data calibration is discussed in Chapter 4, editing is discussed in �4.3.5 and �8.1, and imaging and self-calibration are also discussed in �8.4 for spectral-line data and in �9.7 for VLBI data.