# A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Astro*Dictionary by Michael Erlewine





1 article for "Pogson, Norman Robert"

Pogson, Norman Robert [Astro*Index]


English astronomer. Born at Nottingham. Hipparchus divided the stars into 6 magnitudes, according to their brightness. Pogson noted, in 1850, that an average 1st magnitude star was about 100 times brighter than a 6th magnitude star, and suggested that this difference be used as a standard measuring scale. Thus, each change of one unit on the magnitude scale represents a change in the ratio of brightness which is equal to the 5th root of 100, or 2.512. The magnitudes of various bodies are normally given to the nearest tenth, or hundredth, and extend into negative numbers for the brightest members of the Solar System. For example, the magnitude of the Sun is - 26.91, Sirius is -1.58.


Astro*Index Copyright © 1997 Michael Erlewine