NASA’s More Accurate Eclipse Maps

A map showing the umbra (the Moon’s central shadow) as it passes over Cleveland at 3:15 p.m. local time during the April 8, 2024, total solar eclipse. (NASA SVS/Ernie Wright and Michaela Garrison)
NASA SVS/Ernie Wright and Michaela Garrison

For the 2017 solar eclipse, NASA published eclipse maps that took the irregular umbral shadow of the moon into account: the umbra is neither circular nor oval but irregular—more polygonal—thanks to the uneven topography and elevation of both the moon and the earth. Not accounting for that introduces errors into the map that could make the difference between observing a partial rather than a total eclipse. The process behind those more accurate eclipse maps, which involves computer processing of both lunar and terrestrial elevation models, has now been published in The Astrophysical Journal. [Bad Astronomy]