How a Birth-Sky Star Map Is Calculated (And Why Yours Is Unique)

You'll see a lot of "star map" prints online, but most are pretty generic: a stock celestial chart with your name slapped on top. The map on a Zodiac Star-Map Medallion is different. It's computed star-by-star from the real night sky above the exact place and moment you were born. Here's how that actually works.

Step 1 — your birth coordinates

When you give us your place and time of birth, we convert that into precise observer coordinates: latitude, longitude, and a UTC timestamp. A city name like "Buenos Aires, Argentina" becomes geographic coordinates like 34.60° S, 58.38° W. The exact spot matters — a person born in São Paulo sees a meaningfully different sky than one born in Lima, even at the same instant.

Step 2 — what's overhead at that moment

We then ask: which stars were visible above the horizon at that observer's location on that exact moment? This involves rotating the celestial sphere to the local sidereal time, then computing each star's altitude and azimuth. Stars below the horizon are dropped. The result is a true horizon-up view of the actual sky over your birth spot.

Step 3 — the star catalog

The stars themselves come from a professional astronomical catalog containing positions and apparent magnitudes for the brightest naked-eye stars. We render them at their real positions, scaled by brightness, so the bright constellations (Orion, the Big Dipper, Scorpius) appear as recognizable patterns — not random dots.

Step 4 — translating physics into a printable design

The final step is design: we trace the constellation lines you'd see in a stargazing app, frame the visible hemisphere in a clean circular boundary, and add your name + date + birthplace coordinates around the rim. Then we hand the layout to the printer.

Why this is harder than printing a poster

A printed poster can use any star map and nobody knows. A 3D-printed relief medallion is unforgiving: every constellation line is physical, raised in plastic. The geometry has to be right or it looks wrong. That's why we do the math properly — the night sky over Buenos Aires at 10:00 PM on March 3, 1970 is not interchangeable with anyone else's.

That's the whole point. Your star map is a real, physical artifact of a specific instant in history — the moment you arrived.

Design yours →