Twenty-five minutes of open sky

What the noise was hiding

A single frame is a grey rectangle with a few dozen stars in it. Registered on the star field and averaged, the random noise falls away by about twelve times and the sky underneath appears: the Milky Way running edge to edge, the dark dust lane splitting it on the left, and the small elongated smudge near the top right — the Andromeda Galaxy, the furthest thing a person can see without a telescope.

Twenty-five minutes of the Earth turning

The registration is what holds the stars still; drop it, keep the brightest value each pixel ever reached, and every star draws the arc it actually travelled. Twenty-five minutes buys 6.4° of turn — short enough that these read as dashes rather than the long sweeps of the second night, but long enough that they are visibly concentric, tightening towards a centre just past the right-hand edge.

That centre is the celestial pole, and nothing here was told where it is. It falls out of the frames: the sky's motion across the run is one rigid rotation, and the axis of that rotation is the pole. The red dashes running down the right are not a star — that is an aircraft, ticking off its anti-collision strobe frame after frame.

Everything that crossed, all at once

Every trail found in every frame, laid back over the deep stack. The long continuous lines are satellites; the dashed ones are aircraft, given away by their red anti-collision strobes. Several satellites appear in five, seven, nine frames in a row, marching a little further along the same line each time — which is exactly the pattern that reads as the same shooting star in different positions when you flick through the shots.

Everything, at full size

PNGs are 16-bit and unclipped, so they take an edit better than the JPEGs do. All of it is free to use however you like.

File	What it is	Download
01_milkyway_stack	Deep stack, all 153 frames	PNG 16-bit 19 MB JPEG 3 MB
02_star_trails	Star trails, 6.4 degrees of rotation	PNG 16-bit 22 MB JPEG 2 MB
03_night_traffic	Every detected trail over the deep stack	PNG 16-bit 19 MB JPEG 3 MB
04_timelapse	Timelapse — re-encoded to 1600 px to fit the host's 25 MiB cap	MP4 13 MB
05_what_crossed_the_sky	Labelled close-ups: aircraft, satellites, candidate	PNG 16-bit 11 MB JPEG 1 MB

All 153 frames, one image

What the noise was hiding

The same 153 frames, not registered

Twenty-five minutes of the Earth turning

Everything that crossed, all at once

Originals

Everything, at full size