Astrarium

Now on Apple Watch: tonight's sky and a star chart on your wrist. Pick your site on a map, and see the whole sphere with the new Aitoff projection.

Choose a place and a time, and Astrarium draws that sky. Every position is computed on the device, so the whole app works where there is no signal.

CATALOGUES (all bundled) • 9,096 stars — Yale Bright Star Catalogue, to about magnitude 8: everything the naked eye can see • 155 nebulae, clusters and galaxies — the Messier and Caldwell objects, with photographs and descriptions • The 88 IAU constellations: 752 line segments from the official IAU figures, and the classical constellation art • The Milky Way, from NASA's Deep Star Maps 2020 — the accumulated light of 1.7 billion stars • Planets and the Moon from JPL DE421, with surface maps, libration, lunar age and the traditional full-moon names • 16 major meteor showers, the MPC observatory codes, observing sites worldwide

WHAT IT DOES • Whole-sky and horizon views, pinch zoom down to a one-arcminute field • Jump to any date, run the clock at up to 6000x, step by the synodic month • Planet close-ups: apparent diameter, phase, geocentric and heliocentric distance, orbital elements, and the moons of Jupiter, Saturn and Mars — tap one for its own figures • Meteor shower calendar: maximum in local time and UT, radiant altitude, moon conditions, and an expected hourly rate from the ZHR and the radiant altitude • Comets and asteroids from the MPC and JPL, plotted on the chart • Satellites: the space stations (ISS and Tiangong) on the chart, with visible-pass predictions. The orbital elements (TLEs) come from CelesTrak; they go stale in a few days, so refresh them with “Download / update TLEs” (everything is computed offline once fetched, and the same group is re-fetched at most once every two hours) • Four coordinate grids, the ecliptic, celestial equator, galactic plane and meridian, and field-of-view frames for smart telescopes and camera lenses • Switch each layer on its own: constellation lines and names, stars, star names, the Sun and planets, deep-sky objects, the Milky Way and the constellation figures — turn the stars off and the figures stand alone • Limiting magnitude that follows twilight and moonlight, a red night-vision mode, PNG/PDF export, a captioned demo, and screen recording

LOCATION Your position is used only to compute the sky where you are, and never leaves the device. If you decline, pick a site from the list or type in the coordinates: nothing is lost.

No ads, no in-app purchases, no account. AR — the chart drawn over the camera image — is included as well. Every source and licence is listed in the app under Credits.

APPLE WATCH Install it on iPhone and it goes to the watch with it. Tonight at a glance — when it gets dark and light again, the Moon's age and rise and set, which planets are up and where, the next satellite pass, any shower running — and a star chart holding the whole sky in one disc, which the Digital Crown moves up to twelve hours either way. The bottom line says how old the figures are, and says so plainly while the iPhone is out of range.