I don't know about Clark, but to us normal mortals, the number of stars you can see on a clear, moonless night, in a dark area away from city lights, is about 2000. This according to a website cosponsored by CalTech and Jet Propulsion Laboratories.
http://www.spitzer.caltech.edu/EPO/cosmic_kids/AskKids/seestars.shtml This fellow, an Australian astronomer, however, disagrees:
How many stars can you see at night?
It seems like millions, but it's less than a thousand! Astronomers measure the brightness of stars in Magnitudes. In a fairly dark suburb on an average night, the faintest star you can see is about Magnitude 5.5.
There are about 2,800 stars visible down to a brightness of Magnitude 5.5. Of course, these stars surround the entire globe of the Earth, so you'll be able to see only about half of these stars above your local horizon at any given time - say about 1,400 stars.
But there's an effect called "atmospheric extinction", which means that as a star gets low in the sky and close to the horizon, it gets lost from view because the light is absorbed by the extra atmosphere it has to travel through. Also, the number of stars you can see depends on your location. For example, in Australia, we can always see the Southern Cross, while people on the other side of the equator can see the Southern Cross only at certain times of the year, and then, only for a few hours.
At Australia's latitude, we can see more stars than anyone else on the planet - about 950 after dusk, dropping to about 800 in the early morning.
So because we in Australia can see more stars, and at such a convenient time as soon after sunset, perhaps we have a Cosmic Duty to look at the evening sky every night.
http://www.abc.net.au/science/k2/homework/s95624.htm Nan
