  The recent discovery of exceptional seeing conditions at Dome C, Antarctica,
raises the possibility of constructing an optical observatory there with unique
capabilities. However, little is known from an astronomer's perspective about
the optical sky brightness and extinction at Antarctic sites. We review the
contributions to sky brightness at high-latitude sites, and calculate the
amount of usable dark time at Dome C. We also explore the implications of the
limited sky coverage of high-latitude sites and review optical extinction data
from the South Pole. Finally, we examine the proposal of Baldry and
Bland-Hawthorn (2001) to extend the amount of usable dark time through the use
of polarising filters.
