What the sky contains
Haloes, rainbows, the Milky Way, a comet, a nova, meteors, satellites, a fireball: one sight at a time. 13 reconstructions, none of them a video: each is computed while you watch it.
What the sky can hold#
These hold no recorded phenomenon at all. They are skies set up with the conditions one sight needs, for looking at that sight — because most of them need three or four conditions at once, and knowing which is exactly what separates “there was no Milky Way” from “I could not have seen it”.
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Air traffic and trails
Gonesse, 30 December 2025, 16:10 UTC: the aircraft that were really in this sky, from adsb.lol's record. Their lamps, the Sun still lighting them after the ground has lost it, the trail their engines leave where the air aloft allows one, and the sound of those that could be heard. Point at one to read what the record says of it. A compatible candidate, never an identification.
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Cloud layers in motion
Cloud layers you can set — altitude, thickness, coverage, size, density, wind — down to individual clouds driven one by one.
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Ice haloes and sundogs
A cirrus veil, a Sun 20° up, crystals falling level: a hexagonal ice prism and Snell's law give every angle. Then the crystals tumble, the veil thins, a cumulus deck passes under it, and the display changes with each.
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Rainbow
Rain, a Sun 9° up, a gap in the cloud, an observer facing away from it — all four, or nothing. Primary, secondary reversed, Alexander's band between.
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Moonbow
The same geometry under a full Moon 22° up. Too faint for colour vision, so the eye sees a white arc — which is what observers describe.
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The Milky Way
New Moon, Sun 65° down, galactic centre 81° up over the Atacama. Integrated through a real dust model, so the dark rift falls out of the calculation.
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Zodiacal light
Sun 16° below the horizon, no Moon, the Sun's path standing steep over the west: a faint tilted cone of light with blurred edges, gone within the hour.
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A comet
Hale-Bopp at dusk on 1 April 1997, magnitude −0.8, 30° up to the north-west with a 20° tail. The orbit is propagated from that apparition's own elements.
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A new star
Nova Aquilae over Paris, 10 June 1918, 23:30, magnitude 0.2 where nothing shone the night before. Its brightness is interpolated between the AAVSO's own observations.
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A meteor shower
Perseids, 13 August 2018, 04:05, radiant high and no Moon — over the sporadic background that falls every night of the year.
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A Starlink train
Paris, 29 July 2025 at 11 pm, two days after a launch: the new satellites cross in a line, each propagated from the orbital elements archived that day.
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A recorded fireball
Edinburgh, 27 December 2025 at 03:16: a bolide 13 cameras of the Global Meteor Network triangulated, found in its archive and drawn from here as it burned.
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A re-entry
Zond 4's launcher breaking up over Kentucky, 3 March 1968 at 21:45: the burning string that 78 reports turned into a formation, a cigar with windows, a silent craft.