Melding good optics and good astronomy -- Making every photon count!

Gil Moretto
University of Durham, UK

Advancing astronomical knowledge has a close relationship to light
gathering power, but it also depends on how "efficiently" light is
gathered.  I present here a few examples from my own experience which
illustrate what I consider to be the important concepts for new
astronomical instruments and facilities.

Topics including: liquid mirror telescopes; active correctors for fixed 
primary mirror observing up to 22.5 Deg from zenith and a solution for 
tracking liquid mirror telescopes and the new generation of huge and heavy 
50-100M telescopes; new techniques for integral field spectroscopy - where
source's spatial information is preserved - and the new generation of
HIGHEST dynamic range off-axis telescopes for photometry and angular
resolution will be presented.  These examples are intended to corroborate 
our principle of light gathering efficiency: "the more tenuous the  optical 
information is, the more efficient the system should be"!