Asteroid occultation

Shaded: the path, as wide as the asteroid, and darkest down the middle where the star stays hidden longest — at the edges it barely blinks. Dashed either side: one standard deviation, and beyond it the finer dashes are two. The dotted line is the rest of the track around the world. Labels along the centre line are the time the shadow passes there. Tap the map, or drag the pin, to put your spot anywhere — everything on this page follows it.

The numbers

Everything here is computed for the place in the chip above: the time is when the shadow passes closest to you, and the chord and fade are what you would record there. The asteroid is a sphere of its catalogue diameter, so a real, lumpy one casts a slightly different shadow — which is exactly what timing it from several places measures.