Tables 5 and 6 provide the roadmap to the next generation facility with which the CFH community should be involved. It is clear from these that the one ground-based telescope that will most impact the science goals that we have recognized is a very large instrument optimized for imaging and spectroscopy. The NGC committee is of course not alone in thinking along these lines. One group which is well advanced with such a project is ESO whose OWL initiative envisions a telescope in the 25 - 100m range. NOAO very recently commissioned a study of future telescopes for its community (MAX-AT), the conclusion being that the US astronomers will require a telescope with an aperture in the range of 30 - 50m.
A large telescope such as a 25m one would have to operate with full adaptive optics correction, for which several solutions have been proposed, including tomography. This technique, widely used in medical imaging, is still in its infancy in its application to adaptive optics. It uses the different beam illumination from a few natural stars to reconstruct the wavefront. In principle, this technique works best for larger diameters (i.e. larger air column over the telescope for better modelling of the atmosphere) but at the moment, it is not clear what the minimum diameter of the primary mirror should be to be able to apply the tomography technique. This could be a key driver in the choice of aperture for the NGC and can only be decided upon after a detailed study.