•Ancient
system created by Hipparchus
–1st magnitude = brightest stars in sky
–6th magnitude = faintest visible to naked
eye
–Confusing
because smaller number implies brighter
•(Think
of first magnitude as “first in class”)
•
•Astronomers
want a numerical measure of
Intensity
(I) which is proportional to energy per unit time received from the star.
•
•Relationship between I and m turns out to be “logarithmic”
(result of properties of human eye)