An epic canon of eclipses

One of the 160 maps in the Canon der Finsternisse showing eclipses from 2008 to 2030

One of the 160 maps in the Canon der Finsternisse showing eclipses from 2008 to 2030

Among eclipse cognoscenti, the Canon der Finsternisse (Canon of eclipses) by Theodor von Oppolzer (1841-1846) stands alone in the pre-computer era as the epic compendium of eclipse calculations and maps spanning over three millenia. 

Theodor von Oppolzer was a mathematician, geodesist, and astronomer and published many papers with computations for orbital elements of asteroids and comets. Oppolzer observed the solar eclipse of 1868 August 18 and was inspired by this event to begin the calculations of solar eclipses which culminated in his Canon nearly 20 years later. Oppolzer organized a group of ten human computers to divide the task of calculating 8000 solar eclipses and 5200 lunar eclipses. For each solar eclipse, points were calculated for the begin, end, and mid-point of eclipse and circular arcs were drawn between the three points, resulting in considerable inaccuracies in the geographic locations of eclipse paths.  

Within the Canon, the circumstances of the solar eclipses were summarized in a set of 160 tables with correlating maps. Each table and map represents a set of 50 successive solar eclipses. The fact that each table and map contains exactly 50 eclipses explains why they span irregular intervals of about 20 years, plus or minus a year or two.

Sadly, Oppolzer did not live to see the completion of his opus; he died the year before its publication. He is reported to have inspected the final proof-sheets of the Canon in the hours before his death at the age of 45.

The original Canon der Finsternisse is exceedingly rare and is found only within university or observatory libraries. In 1962, the Canon was reprinted by Dover Publications and translated into English by Donald Menzel and Owen Gingerich. I was fortunate to meet Owen Gingerich during the 2012 transit of Venus upon Mount Wilson, California and have his signature inside the front cover of my copy of the Dover edition.