BSL Astronomy Glossary - dark adaptation - definition
Definition: Dark adaptation allows our eyes to see things more easily in the dark. When we go outside on a very dark night, it is difficult, at first, to see anything. After about 15 minutes it becomes easier to see the stars clearly. When there is not enough light, our pupils quickly dilate and become larger, allowing more light to enter the eye and enabling us to see more easily in the dark.