  A practical evaluation of the Multi-Scale CLEAN algorithm is presented. The
data used in the comparisons are taken from The HI Nearby Galaxy Survey
(THINGS). The implementation of Multi-Scale CLEAN in the CASA software package
is used, although comparisons are made against the very similar
Multi-Resolution CLEAN algorithm implemented in AIPS. Both are compared against
the classical CLEAN algorithm (as implemented in AIPS). The results of this
comparison show that several of the well-known characteristics and issues of
using classical CLEAN are significantly lessened (or eliminated completely)
when using the Multi-Scale CLEAN algorithm. Importantly, Multi-Scale CLEAN
reduces significantly the effects of the clean `bowl' caused by missing
short-spacings, and the `pedestal' of low-level un-cleaned flux (which affects
flux scales and resolution). Multi-Scale CLEAN can clean down to the noise
level without the divergence suffered by classical CLEAN. We discuss practical
applications of the added contrast provided by Multi-Scale CLEAN using two
selected astronomical examples: HI holes in the interstellar medium and
anomalous gas structures outside the main galactic disk.
