The Night We Met — an Anniversary Star Map
The bar, the party, the train platform — wherever it happened, there was a sky over it. Rebuild it from three facts: the date, roughly when, and where.
Recreate your night
Free, in your browser — no account, nothing uploaded. Both downloads are the complete chart: a vector SVG and a 300 dpi PNG, with nothing held back and nothing to buy.
An anniversary star map works because it is specific. Not “a starry sky” — that sky: the constellations that stood over that city at that hour, computed from a star catalog rather than painted on.
Getting the details right
- The after-midnight trap: if the night ran past midnight, the moment you remember may belong to the next calendar date. “The night of June 14th” at 1 a.m. is June 15th on the form.
- Place beats precision: use the city where it happened. Street-level coordinates change the chart imperceptibly; the city changes it a lot.
- Time can be approximate: the sky drifts ~15° per hour. “Around eleven” is plenty.
How the map is computed
You give it three things: a date, a time, and a place. For the place, type a town or city name and pick it from the list — 29,919 towns and cities of 18,000 people or more, from GeoNames — or enter an exact latitude and longitude instead. Accents are optional (“malmo” finds Malmö), but type the name on its own: “Roskilde Denmark” finds nothing, and a typo finds nothing rather than the wrong sky.
Your date, time and place are converted to a Julian Date and then to local sidereal time — the astronomer’s clock for “which way is the sky facing.” Each of the 1,630 stars in the Yale Bright Star Catalogue (every star brighter than magnitude 5.0, i.e. every star a good naked eye can see) is transformed to its altitude and azimuth at that exact moment, and every one of those stars above the horizon is projected onto the circular chart: zenith at the centre, horizon at the rim, north at the top — and east on the left, because a star map is read looking up, which mirrors east and west compared to a ground map.
The 89 constellation figures are drawn with the same math and clipped at the horizon. Star dots are scaled by real brightness (magnitude) and tinted by star colour. The Moon is drawn at its real altitude, azimuth and phase for your moment, and left off entirely when it was below your horizon. It does not show the planets, comets or satellites — those wander against the fixed stars and need ephemerides, which this version does not compute. Everything runs in your browser — nothing is uploaded, there is no account, and the page works offline once loaded.
Common questions
We don't remember the exact time — does it matter?
Not much. Across a single evening the visible constellations change slowly; an hour of uncertainty rotates the chart slightly without changing its character. Pick the hour that feels right.
We met in one city but live in another — which one do I enter?
The place where the moment happened. The map is a portrait of that night there, not of where the print will hang.
It was cloudy that night. Is the map still honest?
Yes — the chart shows the stars that stood above the clouds. They were there whether or not you could see them, which is rather the point.