Check our work. Please.

Up to 2,000 of the brightest stars, each in its true position — computed from the Hipparcos/HYG catalogs (the standard data professional astronomers use) and verified against the U.S. Naval Observatory to within a fraction of a star’s width. Here is exactly what that means.

The star data

Every chart plots stars from the HYG database, a compilation built on the Hipparcos satellite catalog — the standard reference for star positions and brightness. From a catalog that runs to the naked-eye limit, we draw the brightest 2,000 stars above your horizon at your exact moment, sized by true magnitude, with constellation lines traced through the actual member stars.

The time and place

Your date is interpreted in the time zone of the place on the map, never your browser’s clock. Daylight saving, historical zone changes, and the hemisphere are resolved from the coordinates themselves, so “10 pm in Paris, 14 Feb 2019” means exactly that instant, whether you order from Texas or Tokyo.

The verification

We cross-check our engine’s computed positions against the U.S. Naval Observatory’s published ephemeris — the reference celestial navigators steer by — and hold agreement to within a fraction of a star’s printed width. Those assertions run as automated tests on every change to the engine: the chart you buy is produced by code that has to prove itself before it ships.

Why nearby dates look similar

The honest footnote: the fixed stars shift by only about one degree per night, so two dates a few days apart genuinely produce near-twin charts. That’s the real sky, not a shortcut. Across weeks and months the sky transforms completely — and your exact date, time, and coordinates are printed on the poster either way.

Found something that looks off? We want to know: hello@ourfirstsky.com.