Horizon vs Astrelia

Hold up your phone and watch the night sky come alive. Horizon-AR uses your camera, GPS, and device motion to place real-time augmented reality overlays exactly where celestial objects appear in the sky above you. TRACK THE SOLAR SYSTEM Follow the Moon, Sun, Mercury, Venus, Mars, Jupiter, and Saturn with a live arc overlay showing each object's full path across the sky tonight. Rise and set times update in real time based on your precise location. 110 MESSIER DEEP-SKY OBJECTS IN AR Activate Hot Targets mode and see every Messier object currently above your horizon floating in the AR view — galaxies, nebulae, open clusters, and globular clusters, each colour-coded by type. Tap any label to open a detail card showing: • Object type and Messier catalogue number • Common name (Andromeda Galaxy, Orion Nebula, Pleiades…) • Current altitude above the horizon • Apparent visual magnitude • Recommended instrument — naked eye, binoculars, or telescope • Favourite toggle, saved across sessions When objects cluster together, a single tap fans them out radially so you can reach each one individually. FILTER BY OBJECT TYPE Narrow the Hot Targets overlay to just galaxies, just nebulae, or just star clusters with a single tap. Objects you've starred appear in your Nightly Overview for quick access every session. FREEZE THE SKY Long-press anywhere to lock the entire AR view — overlays and camera image — as a still frame. Perfect for star parties, sketching, or sharing a screenshot. Tap once to unfreeze. NIGHTLY OVERVIEW Open the Tonight sheet for a full list of rise, transit, and set times for all solar system objects plus your Messier favourites, sorted for the coming night at your location. WORKS WITHOUT FULL PERMISSIONS No camera access? Horizon-AR switches to a star-field background with altitude rings and an azimuth grid so you can still explore the sky. Declined location? Enter coordinates manually and continue without interruption. No account. No subscription. No ads. Privacy: your location and camera data never leave your device.

Raise your phone toward the sky and Astrelia shows you what is actually up there: stars, planets, the Moon and the Sun, placed for your exact location and this exact instant. Tap anything and it tells you everything it knows. POINT AT THE SKY Around 8,900 naked-eye stars, sized and coloured the way the eye sees them. Constellation lines, the ecliptic with the live planets, and a Sun and Moon computed with topocentric parallax and atmospheric refraction, so they sit where you can genuinely see them. Pinch to zoom and more names appear. Tap any star to identify it. Scrub time twelve hours forward or back and watch the whole sky move. Aim at something bright and align, and the compass error that ruins most sky apps is cancelled out. TONIGHT One screen for what is happening: the Moon's phase, sunrise and sunset, which planets are up right now and which are below the horizon, meteor showers near their peak, and what is coming — eclipses, oppositions, solstices, greatest elongations. All of it searched out of the live ephemeris, not read from a hardcoded list. NUMBERS THAT MEAN SOMETHING Every object opens into real astrophysics: distance, spectral class, temperature, luminosity, derived radius, orbital elements. Next to them, plain language — the year the light you are looking at left that star, how many Suns it would take to match it, what you would weigh on that planet, where the star falls on the HR diagram, and a one-line biography of its life. Anything unfamiliar has a glossary entry a tap away. THE GALAXY MAP Leave Earth entirely and free-fly a 3D map built from real data: about 25,000 catalogued stars at their true distances, the Milky Way as its real barred spiral, and deep-sky landmarks at their real positions, distances and sizes. Twenty-seven nebulae are built from public-domain telescope photographs, so their shape and colour are the ones the telescope saw — fly into them and they hold up in three dimensions. Fly to a star and its confirmed exoplanets are there, orbiting it. At the galactic centre, Sagittarius A* is rendered by tracing light through curved spacetime: the galaxy behind it genuinely bends around it. CONSTELLATIONS All 88 IAU constellations, plus asterisms, historical figures and cultural skies, each drawn over its real stars. Open any of them in 3D and the familiar shape falls apart into deep space, because a constellation is a line of sight rather than a thing. Astrelia computes all of it on your device from catalogs that ship inside the app. No account, no subscription, no ads, no tracking, and no network needed to use it. Every dataset, algorithm and image behind it is credited in About → Sources. Astrelia has a sister app, Selenia, which reads the same real sky the astrological way.