Why do nocturnal animals usually have large pupils in their eyes? How is that related to astronomical telescopes?

Pupils. The pupil is a structure in the front of the eye that regulates how much light reaches the retina at the rear ... In the dark, the pupil relaxes, becoming larger to let in as much light as possible. Nocturnal animals generally have pupils that can open wider than those who thrive in the daylight hours. Seeing the Universe at Different Wavelengths. Although optical telescopes are the type most commonly used for stargazing and amateur astronomy, lots of astronomical research is done on telescopes that look at other wavelengths of light.