What's real here, and what's stylised

Every position, phase, rise/set time, and distance in the app is computed locally in your browser with the open-source astronomy-engine library, which implements VSOP87/ELP-derived planetary and lunar models. Nothing is fetched from a paid astronomy API, and nothing is estimated by eye — when a calculation can't be produced reliably, the app says so rather than showing a made-up number.

Positions are computed for an observer at your chosen location's latitude and longitude, at sea level. Every clock time shown — rise/set times, the current moment, trigger windows — uses the IANA time zone resolved from that location, not your device's zone, with daylight-saving handled automatically. If a zone can't be resolved for a coordinate, the app falls back to your device's zone and says so.

Altitude/azimuth for the Sun, Moon, and visible planets are computed for your exact location and moment, then adjusted for standard atmospheric refraction near the horizon — the same "normal" refraction convention used throughout the app, including the ecliptic overlay, so drawn objects and the drawn ecliptic line agree with each other near the horizon. Refraction is a well-established average correction; it does not account for unusual local weather.

Background stars are drawn from a real packed star catalog shipped with the app (J2000 equatorial positions, magnitude, and color index), not randomly generated points, and they default to off so they never compete with the solar-system objects. The ecliptic overlay is calculated independently — it's the true ecliptic plane of date, sampled and rotated into your local sky — rather than a line fitted through the currently visible planets.

The Moon is close enough to Earth that its apparent position shifts measurably depending on where you stand — this is parallax. The app computes the Moon topocentrically, from your specific location, so its drawn position near the horizon reflects that shift rather than treating the Moon as if seen from Earth's center.

The In Space view has two explicit modes. Readable mode compresses distances (using a logarithmic radial transform) so Mercury through Saturn fit on one screen; direction and ordering are preserved exactly, but distances are not to scale. True mode uses actual astronomical-unit distances. In both modes, body sizes are enlarged by orders of magnitude so they're visible at all — distance and size are never simultaneously to true scale in the same view, and the app does not claim otherwise.

Planet and moon surfaces use illustrative texture maps, not live imagery. Several major moons and a handful of asteroids/comets are modeled using published orbital elements; each has a stated valid date range, and the app shows no position for a body outside the date range its model supports, rather than extrapolating silently.

The "spacetime sheet" and orbit-mesh overlays in the In Space view are teaching analogies for how mass curves the paths of nearby objects — not a simulation of general relativity. The visual depth of the well is exaggerated for legibility and does not correspond to a physically accurate curvature at that scale.

The app has no weather, cloud-cover, or light-pollution data, and does not model buildings, trees, or terrain. "Above the horizon" is a geometric statement, not a promise that you can actually see the object from where you're standing — the horizon panorama itself is a schematic, decorative silhouette.

A manually chosen or searched location is as precise as the place you picked. A browser-geolocated position is rounded to four decimal degrees (roughly 11 meters) before it's used or saved. Shared links can be either approximate (about 11 km) or precise, at the sharer's choice — see the privacy page for exactly how that works.

• No camera AR and no compass input — the sky dome is dragged by hand.
• No deep-sky objects (galaxies, nebulae) and no artificial satellites.
• No live weather, cloud cover, or light-pollution modeling.
• No background notifications — watchlist triggers are evaluated only while the app is open.
• The sky dome uses an azimuthal-equidistant projection, which distorts apparent shapes near the horizon even though directions are real.
• The Earth-rotation view's celestial ring shows real directions but a schematic, non-scaled distance.
• Modeled small bodies and moons are unavailable outside their stated valid date ranges.