One of my favorite iPad apps is Emerald Observatory, so when the original developers retired and open sourced the code, I volunteered to take over publishing it as an app in the App Store.

Picture of Emerald Observatory on an iPad

Emerald Observatory displays a wealth of astronomical information all on one screen, in a unique but understandable format. Information includes:

  • 12- and 24-hour ordinary clock time
  • Times of rise and set for the Sun, the Moon, and the 5 classical planets
  • Times of the beginning and ending of twilight
  • Heliocentric orrery (display of the planets in orbit around the Sun)
  • Altitude and azimuth for the same bodies (one body at a time)
  • Current phase and apparent orientation and relative size of the moon
  • Current regions of day and night on a world map
  • The Equation of Time, solar time, UTC time, and sidereal time
  • Month, day, year, and leap-year indicator
  • Daily alarm (delivered as local notification on iOS 4+ if app is not running)
  • Eclipse simulator

The privacy policy is simple: nothing is collected.

All the source code is available on Github (note that the source is five separate packages and that the build infrastructure isn’t entirely obvious; the repos are Observatory, esastro, eslocation, estime, and esutil). You can also find a web version which is maintained by the original developers.

The Github issues system is available for filing bugs and feature requests.