star gaugesSystematic counts of stars in different regions of the sky. They were first made in the 1780s by William Herschel who counted the total number of stars visible in each of several adjoining areas within the region under study. By averaging the sample counts he obtained the star gauge for that region. Herschel compiled star gauges for several hundred regions representative of the northern hemisphere, his work being extended to the southern hemisphere by his son John. This provided the first precise information on the local distribution of stars in the Galaxy. By comparing gauges made to different limiting magnitudes (using larger and larger telescopes) they were able to show that the star system extends to great depths in directions toward the Milky Way. See also source count.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006