Apparent magnitude was first proposed by Hippocrates, an ancient Greek astronomer. He divided the 1022 stars in his catalog into six grades according to brightness, namely 1 star to 6 stars. 1850, the British astronomer Thompson found that the star of 1 is 0/00 times brighter than the star of 6/kloc-0. According to this relationship, the magnitude is quantified. After redefining the magnitude, the brightness difference between each level is 2.5 12 times, and the apparent magnitude of 1 lux (brightness unit) is-13.98.