  Interferometry is a powerful technique for making sensitive, high-fidelity
images of the sky, but is limited in its ability to measure extended or diffuse
emission. Better images of extended astronomical objects can be obtained by
mosaicking together many pointings of the interferometer array. Even better
images can be obtained by combining these data with data from a single-dish
telescope. This lecture explains commonly practiced techniques for obtaining
and analyzing these observations, and the theory behind them.
