  We discuss the optimal detection of point sources from multiwavelength
imaging data using an approach, referred to as MDET, which requires no prior
knowledge of the source spectrum. MDET may be regarded as a somewhat more
general version of the so-called "chi squared" technique. We describe the
theoretical basis of the technique, and show examples of its performance with
four-channel infrared broad-band imaging data from the WISE mission. We also
discuss the potential benefits of applying it to the multifrequency data cubes
of the ASKAP surveys, and suggest that it could increase the detection
sensitivity of searches for neutral hydrogen emission at moderately high
redshifts.
