Cosmic Atlas

An ephemeris in your pocket, measured against NASA to within 28 arc-seconds.

largest deviation from NASA JPL Horizons, across 30 measurements: 28″
lines of C in the ephemeris engine: 13k
on-device calculation modules: 380+

Cosmic Atlas is an ephemeris and birth-chart calculator for iPhone and iPad. Planet positions are computed on the device itself, by an open-source astronomy engine compiled into the app from its C source.

Its accuracy is measured rather than claimed. The engine's output is checked against NASA JPL Horizons, and all thirty measurements are published on the site, together with the caveats.

What is in it

01Built on astronomy-engine, an MIT-licensed open-source library, compiled from C and bridged into React Native through native modules.
02Ten bodies at three epochs compared with NASA JPL Horizons: mean deviation 14.4 arc-seconds, largest 28.
03Nine validation gates, eight of them against a reference outside the project — 305 tests in all.
04Calculation runs on the device, in flight mode, without an account.
05A 3D sky dome and chart wheels rendered with Skia and Reanimated.

Screens

kozmikatlas.com runs the same engine version in the browser.