Magnitudes The magnitude scale was invented by an ancient Greek astronomer named Hipparchus in about 150 BC He ranked the he could see in terms of their brightness, with 1 representing the brightest down to 6 representing the faintest. Modern astronomy has extended this system to stars brighter than Hipparchus' 1st magnitude stars and ones much, much fainter than 6. As it turns out, the eye senses brightness logarithmically, so each increase in 5 magnitudes corresponds to a decrease in brightness by a factor 100. The absolute magnitude is th ....