Dark adaptation
The way your eyes slowly become more sensitive in the dark, letting you see faint stars and meteors.
When you step outside from a bright room, the sky at first looks almost empty. Wait, and more and more stars appear. This is dark adaptation. Your pupils open wider within seconds, but the bigger change is inside your eyes: special light-detecting cells called rods slowly become much more sensitive. It takes about 20 to 30 minutes to get most of your night vision, and it keeps improving a little after that.
Good dark adaptation can mean seeing many more meteors during a shower, because most shooting stars are faint. The trouble is that a single glance at a bright phone screen, torch or car headlight can undo much of your progress in moments.
Here's how to protect your night vision. Give yourself at least 20 minutes in the dark before you start counting. Use a dim red light, perhaps a torch covered with red cellophane, to read charts, because red light disturbs night vision the least. Turn your phone's brightness right down or use a red-screen mode. Always take an adult with you and stay somewhere safe. And remember: never look at the Sun, with or without binoculars, because it can blind you.
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Level: Beginner Ages 7 and up