How good is the night sky?

The square of Pegasus is a familiar landmark in the night sky at the moment, They say that you can judge how good the viewing conditions are by how many stars are visible in the square. I can see about half a dozen on a good night in Wigton. There is the added problem of how ours eyes work. They rod cells round the outside are better light detectors than the cone cells in the middle of the eye. So I can sense more stars inside the square but as soon as I look directly at them, the cone cells take over and the stars disappear because they are too dim to be detected by cone cells.