The apparent magnitude of a celestial object is a number that is a measure of its brightness as seen by an observer on Earth.
Aristotle (Ἀριστοτέλης Aristotélēs,; 384–322 BC) was an ancient Greek philosopher and scientist born in the city of Stagira, Chalkidiki, in the north of Classical Greece.
Cone cells, or cones, are one of three types of photoreceptor cells in the retina of mammalian eyes (e.g. the human eye).
The fovea centralis is a small, central pit composed of closely packed cones in the eye.
Messier 41 (also known as M41 or NGC 2287) is an open cluster in the Canis Major constellation.
Peripheral vision is a part of vision that occurs only on the side gaze.
The Purkinje effect (sometimes called the Purkinje shift) is the tendency for the peak luminance sensitivity of the human eye to shift toward the blue end of the color spectrum at low illumination levels as part of dark adaptation.
Rod cells are photoreceptor cells in the retina of the eye that can function in less intense light than the other type of visual photoreceptor, cone cells.
Scotopic vision is the vision of the eye under low-light levels.