Visualizing the moon's shadow across the Earth's surface.
The "path of totality" is a narrow track on the Earth's surface swept by the moon's dark inner shadow (the umbra). While a partial eclipse can be seen across thousands of miles, the total phase is only visible within this narrow corridor, typically just 50 to 100 miles wide.
Mapping an eclipse requires calculating the exact intersection of a cone (the moon's shadow) with an oblate spheroid (the Earth). We use advanced Besselian elements to plot these paths with pinpoint accuracy.
The duration of totality varies along the path, reaching a maximum near the midpoint. Our maps highlight these duration contours to help eclipse chasers find the optimal viewing locations.