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The sky of the night you were born: an n8n workflow recalculates the stars

· Daniele Michelin · ~2 min read · Also in DE · IT

Enter a date, an optional time and a city, and get a poster of that night's sky: stars, moon phase, visible planets, weekday, days lived, weather and three events “on this day”. The astronomy is computed by a Code node inside n8n.

#n8n #ai #automation #data

Topics: AI, LLMs & RAG

daniele@mikweb: ~/blog — less n8n-birth-sky.md

Try it first: the sky of your birth night. Enter the date, the time is optional, and the city. A few seconds later the poster is there.

What you get

  • The sky poster: the stars above your city that night, with the 88 constellations, drawn in a canvas.
  • Moon phase and planets: how the moon looked and which planets were in the sky.
  • Numbers: the weekday and how many days have passed since.
  • Weather: on the day you were born and on your last birthday.
  • Three events “on this day”: from Wikipedia.
  • A short portrait: written by an AI from exactly these data.
  • A preview image: for sharing, with the sky as its motif.

The workflow

  • Webhook: receives the date, the optional time and the city.
  • Geocoding: Open-Meteo turns the city into coordinates and a time zone.
  • Three requests in parallel: the weather (archive for the birthday, forecast for the last one), “On this day” from Wikipedia and the star catalogue.
  • Code node with the astronomy: sidereal time, azimuthal projection for the poster, planet positions from the JPL Keplerian elements and the moon from a reduced Meeus formula.
  • AI for the portrait: gpt-oss-120b at IONOS gets only the computed values.
  • Saving: a PHP script receives the result. The page draws the poster in a canvas, the server renders the preview image with GD.

How accurate is the maths?

I tested the Code node against the astronomy-engine library. The largest error is 0.15 degrees, invisible on a poster. The star catalogue comes from Yale/Hipparcos via d3-celestial (BSD-3): 2061 stars down to magnitude 5.2 and the 88 constellations.

Honest limits:

  • The planets are approximations from orbital elements, not precision ephemerides.
  • There is no refraction, so no correction for the bending of light in the atmosphere near the horizon.
  • Historical time zones and daylight saving depend on the ICU database. For old dates the local time can be off by an hour.
  • Valid for the years 1900 to 2026.
  • Without a time the workflow uses a fixed moment in the night. The sky turns 15 degrees in an hour, so the poster is then an approximation.

Privacy

The result is stored for 30 days and can be deleted earlier. No IP address is stored, and the result pages are set to noindex.

Build it yourself

The workflow is ready as JSON to import. Open-Meteo and Wikipedia need no key. For the AI any OpenAI-compatible API will do, and for saving you need a small endpoint of your own. More workflows to click and download are on the n8n overview, for example the Website DNA scan.

Now it is your turn: what was the moon phase on the night you were born? Tell us in the comments.

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