Why do my eyes need time to get used to the dark?
Your eyes slowly adjust to darkness, opening your pupils and making special light-catching chemicals. After about 20 to 30 minutes, you can see many more stars and meteors.
When you walk from a bright room into the dark garden, at first you can hardly see anything. But wait a while, and stars, trees and paths slowly appear. This is called dark adaptation.
Two things happen in your eyes. First, the black hole in the middle of each eye, the pupil, grows wider to let in more light. That takes only a few seconds. Second, and much more slowly, special cells at the back of your eye, called rods, build up a light-sensitive chemical. Rods are brilliant at seeing in dim light, but bright light uses up their chemical, and it takes about 20 to 30 minutes to rebuild.
That is why meteor watchers wait patiently before starting to count. After your eyes are fully adapted, you can see far fainter meteors and many more stars.
Even a quick look at a bright phone screen or a white torch can undo much of the adaptation, so you have to start waiting again. Many astronomers use red torches, because red light does not affect the rods very much. You can make one by covering a torch with red cellophane or a red balloon. Rods do not see colour well, which is why things look grey in the dark.