Image Fidelity

by Stephan W. Witz last modified Jul 06, 2012 by Stephan Witz

With conventional external calibration methods, even under the best observing conditions, the achieved dynamic range will rarely exceed a few hundred. The limiting factor is most often the atmospheric phase stability, although pointing errors and changes in atmospheric opacity can also be a limiting factor.  If the target source contains compact structures of sufficient strength (depending on the band, bandwidth, atmospheric coherence time, and source complexity), self-calibration can be counted on to improve the images.  Dynamic ranges in the thousands to hundreds of thousands can be achieved using these techniques, depending on the underlying nature of the errors. With the new WIDAR correlator and its much greater bandwidths and much higher sensitivities, self-calibration methods can be extended to observations of sources with much lower flux densities than very possible with the old VLA.