[Engraved-on-His-hands]

The Pleiades is a good object to illustrate an anomaly of our vision. Our eyes cannot collect the most light when looking straight ahead, but when looking slightly to the side. You might be able to see a certain number of stars in the Pleiades (perhaps 5 to 8) on a clear night when looking straight at it, but you might be able to see another star or two when you look slightly to the side and catch it “out of the corner of your eye”, so to speak. Try it. It works.

[SunkenCiv]

Thanks!

[BatGuano]

The phenomena that you describe is due to the structure of the human eye. Basically the receptors in the eyes are cells that are rod shaped and cone shaped. The cones are in the center and the rods at the edge. You use the cones in good light and the rods in poor light conditions.

To illustrate this, toss a ball into the air in poor light, after dusk. If you try to look directly at the ball, you will not catch it. Look to the side and you, using the rods, will see it more clearly and be able to catch it!

[Nowhere Man]

The Pleiades is a good object to illustrate an anomaly of our vision. Our eyes cannot collect the most light when looking straight ahead, but when looking slightly to the side. You might be able to see a certain number of stars in the Pleiades (perhaps 5 to 8) on a clear night when looking straight at it, but you might be able to see another star or two when you look slightly to the side and catch it “out of the corner of your eye”, so to speak. Try it. It works.

I remember Carl Sagan told the same story in hos book, "Cosmos" where back in 1957, as a graduate student, he got a phone call from a man who saw a comet but when he looked direct at it, it disappeared but if he turned his eyes away slightly, he can see it. I've noticed it myself too.