  For the majority of optical observing programs, the sky brightness provides
the fundamental limit to signal detection such that the scientific feasibility
is largely dictated by the moon phase. Since most observatories do not have the
resources to build expensive high-resolution or infrared instruments, they are
increasingly at a loss as to how to exploit bright time. We show that, with due
consideration of the field and moon position, it is possible to undertake `dark
time' observing programs under `bright time' conditions. Our recommendations
are particularly appropriate to all-sky survey programs.
  In certain instances, there are gains in observing efficiency with the use of
a polariser, which can significantly reduce the moonlight (or twilight)
sky-background flux relative to an extraterrestrial flux. These gains are
possible in background-limited cases because the sky background can be highly
polarised, due to scattering, around ninety degrees away from the moon (or
sun). To take advantage of this, only minor modifications to existing
instruments are needed.
