The fix for a wobbly sky: shoot thousands of frames, keep the lucky ones

Point a telescope at the sky and the atmosphere gets the last word. Pockets of air at different temperatures and densities drift around and bend light on its way to the ground, which is why astronomy images come out smeared instead of sharp.

The workaround described in NASA's Astronomy Picture of the Day is called lucky imaging: a high-speed camera captures thousands of very short exposures in quick succession, and the clearest frames are then added up into the final picture. The technique trades time for luck — the photographer isn't correcting the blur, just collecting the instants when the air cooperated.