The Scheinergrade (Sch.) system was devised by the German astronomer Julius Scheiner (1858–1913) in 1894 originally as a method of comparing the speeds of plates used for astronomical photography. Scheiner's system rated the speed of a plate by the least exposure to produce a visible darkening upon development. Speed was expressed in degrees Scheiner, originally ranging from 1° Sch. to 20° Sch., where an increment of 19° Sch. corresponded to a hundredfold increase in sensitivity, which meant that an increment of 3° Sch. came close to a doubling of sensitivity. COUNT 5
QSN1 Who created the Scheinergrade system?  ANS1 the German astronomer Julius Scheiner QSN2 What is the Scheinergrade system used for? ANS2 comparing the speeds of plates used for astronomical photography QSN3 What do degrees Scheiner indicate? ANS3 the speed of a plate QSN4 What is the range of Scheiner speeds? ANS4 from 1° Sch. to 20° Sch QSN5 Approximately how many degrees indicate double the sensitivity?  ANS5 an increment of 3° Sch