Oh, and one more thing....
Perhaps, if you really can image as faint as 33 magn. per square arcsecond, you could be doing surveys in order to discover ultra-faint dwarf galaxies which are so dominated by dark matter that their luminous component is composed of the merest smattering of faint stars:
http://www.physics.mcmaster.ca/Fac_H...sityDwarfs.pdf
These extremely low-luminosity dwarf galaxies are the objects that are closest in their properties to the tiny "dark matter halos" that have been predicted in cosmological simulations.
The so-far discovered 'dark galaxies' do emit some extremely-extremely-low surface brightness light from a handful of constituent stars, but only a tiny fraction of the total mass of one of these galaxies is in the form of ordinary luminous matter.
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