Seeing Stars II

StarDate

When you walk from a brightly lit room into a dark one, you might stumble for a while until you can see what you’re doing. And the same thing happens when you step out under a dark night sky – it takes some time to see its full glory.

When you enter the darkness, your eyes adapt in several ways. First, the pupil opens wider, letting in more light. Second, the eye’s cones become more sensitive. They see color and detail, but they’re not very helpful when it’s dark.

Finally, the rods adapt. They see best under low light. But they need a special chemical to do that. The chemical goes away when it’s bright. It rebuilds when it turns dark, but it takes time – 20 to 30 minutes.

So if you’re watching the stars from your back yard, turn off the lights, and leave your phone alone. If you need some extra light, try a red flashlight – it won’t mess with your eyes.

One other thing that can enhance your view is averted vision. The rods are concentrated around the edge of the eye, so they do a better job when you look at a faint object out of the corner of your eye instead of straight on.

Two good targets for averted vision are in view by about 8:30 or 9. The Pleiades star cluster is low in the east-northeast, and looks like a tiny dipper. High above it is the Andromeda Galaxy, which looks like a tiny cloud. It’s the most-distant object that’s easily visible to the eye – but only when the eye is ready for the darkness.

Script by Damond Benningfield