Astro Camera

Every 10 minutes of the night, registered on the stars and averaged with aircraft clipped out: the faintest stars and the Milky Way's dark lanes. The steps below show how it was made. · full-res

Sky brightness of every frame (log₂: one stop is twice the light). Dusk and dawn are the slopes at each end; cloud shows as a bump. The star-trail stack uses only frames within 30% of the darkest 10 minutes, so twilight and cloud are left out of it. Left out is not thrown away: those frames still go into the videos.

The raw night: a 10 minute stack sliding on 1 minute per video frame. Dusk, cloud, aircraft and dawn all show here, five seconds for the whole night. · full-res

The night's smooth glow from streetlights is fitted and subtracted from every frame, and the trees and roof are masked. Star trails wheel round the pole and the Milky Way survives. · full-res

Each frame mapped onto the sky through a fitted model of the lens and turned back about the pole, so stars stay points. This shows the brightest of each window's frames once aircraft are clipped out; the average of the same frames is the deep sky above. · full-res

The brightest value each pixel reached all night: every star draws its trail across the night.