Fit an arbitrary sky (image) model to an existing MS

Fitting a Sky Model to an Existing MS in the UV Domain 20may2015 CASA v4.3.1

This casaguide illustrates how to fit an arbitrary sky image model to an existing MS. Along the way it illustrates how to "get your hands" on the raw visibility data in the python interface and how to compute the Chi-squared of the visibility data to your given model. This could be useful if you have a set of source models you would like to compare in the UV domain, but the models are too complicated to be handled by the set of models provided in CASA's uvmodelfit() task. A couple of ALMA 7-m specific points are illustrated along the way.