# Skyfold > See the sky of any place and moment, plan eclipses and satellite passes, print star maps. Skyfold computes the real sky for any place and time in your browser: 8 920 stars, constellations, the Moon and planets, their rise and set times, twilight, eclipses from 2020 to 2040 and passes of the ISS or any satellite from orbital elements. It turns that sky into print-ready star-map posters, plans shadows from the Sun and counts how far you have travelled through space. All positions come from published astronomy algorithms checked against JPL, USNO and NASA reference values. Skyfold (Sky & space atlas) is a premium app of usefulweb.app (https://usefulweb.app/): a full program that runs in the browser. Its engine is deterministic and the same functions are exposed as tools, so an agent can compute exactly what the app shows. ## Use it - Landing page: https://skyfold.usefulweb.app/ - Workspace (browser app): https://skyfold.usefulweb.app/app - open a project with https://skyfold.usefulweb.app/app#project= or a template with https://skyfold.usefulweb.app/app#template= - Project file format (JSON Schema): https://skyfold.usefulweb.app/project.schema.json - Tutorials: https://skyfold.usefulweb.app/tutorials - JSON API: POST https://skyfold.usefulweb.app/api/v1/tools//calculate (catalog: https://skyfold.usefulweb.app/api/v1/tools) - OpenAPI: https://skyfold.usefulweb.app/openapi.json - MCP (Streamable HTTP): https://skyfold.usefulweb.app/mcp ## Engine tools - [Skyfold Star Map Poster](https://skyfoldstarmapposter.usefulweb.app/): Print the real night sky of any place and moment as an SVG or PDF poster. Part of [Skyfold](https://skyfold.usefulweb.app/) (ownerApp: skyfold). API: POST https://skyfold.usefulweb.app/api/v1/tools/skyfold-star-map-poster/calculate · MCP tool `skyfold_star_map_poster` - [Skyfold Planet and Moon Positions](https://skyfoldplanetpositions.usefulweb.app/): Where the Sun, Moon and planets are, and when they rise and set, for any place and time. Part of [Skyfold](https://skyfold.usefulweb.app/) (ownerApp: skyfold). API: POST https://skyfold.usefulweb.app/api/v1/tools/skyfold-planet-positions/calculate · MCP tool `skyfold_planet_positions` - [Skyfold Local Eclipse Circumstances](https://skyfoldeclipselocal.usefulweb.app/): Solar and lunar eclipses 2020–2040 as seen from your place, with contact times. Part of [Skyfold](https://skyfold.usefulweb.app/) (ownerApp: skyfold). API: POST https://skyfold.usefulweb.app/api/v1/tools/skyfold-eclipse-local/calculate · MCP tool `skyfold_eclipse_local` - [Skyfold Satellite Pass Predictor](https://skyfoldsatellitepasses.usefulweb.app/): When the ISS or any satellite flies over you, and whether you can see it, from TLE elements. Part of [Skyfold](https://skyfold.usefulweb.app/) (ownerApp: skyfold). API: POST https://skyfold.usefulweb.app/api/v1/tools/skyfold-satellite-passes/calculate · MCP tool `skyfold_satellite_passes` - [Skyfold Sun Position and Shadow Length](https://skyfoldsunshadow.usefulweb.app/): Sun angle and the length and direction of a shadow for any height, place and time. Part of [Skyfold](https://skyfold.usefulweb.app/) (ownerApp: skyfold). API: POST https://skyfold.usefulweb.app/api/v1/tools/skyfold-sun-shadow/calculate · MCP tool `skyfold_sun_shadow` - [Skyfold Cosmic Odometer](https://skyfoldcosmicodometer.usefulweb.app/): How far you have travelled through space since a date, frame by frame. Part of [Skyfold](https://skyfold.usefulweb.app/) (ownerApp: skyfold). API: POST https://skyfold.usefulweb.app/api/v1/tools/skyfold-cosmic-odometer/calculate · MCP tool `skyfold_cosmic_odometer` ## Formats - Import: Skyfold project (.skyfold.json), Share link (#project=), Two-line element sets (TLE text, pasted or .txt/.tle file), Coordinates as decimal degrees, DMS, UTM, MGRS, Maidenhead or plus code - Export: Skyfold project (.skyfold.json), Star-map poster: PDF, SVG and PNG, Sky chart and framing chart: PNG and SVG, Calendar (.ics) with reminders, Planner, eclipse and pass tables as CSV, Day-and-night map: SVG, Share link ## Limits - Stars are drawn to magnitude 6.5 without proper motion, double-star separation or the Milky Way band; deep-sky objects such as nebulae and galaxies are not included. - Pluto, asteroids and comets are not computed; Saturn’s magnitude excludes the rings. - Eclipses are limited to 2020–2040; local circumstances do not include the lunar limb profile or terrain, and lunar eclipse contacts come from NASA’s catalogue rather than an own shadow model. - Satellite brightness is not predicted, and passes depend on the age of the elements: re-fetch them for anything more than a few days ahead. - Shadows assume flat ground and a thin vertical object; buildings, hills and slopes are not modelled. - Time zones come from your browser’s built-in data; very recent rule changes may be missing, so a fixed offset such as UTC+2 can be used instead. - The PDF uses standard fonts: titles in scripts beyond Latin-1 (for example Arabic or Japanese) are only exact in the SVG and PNG exports.