The first engine turns a date, time, and observer location into a local sky dome. It uses right ascension and declination values from a small curated star catalog, then rotates those stars into a local horizon view using Greenwich Mean Sidereal Time.
The second engine variant is heliocentric. It places the Sun at the center and computes approximate Mercury-through-Neptune positions from NASA/JPL Keplerian orbital elements. The 3D and poster views use compressed orbit spacing so the outer planets can fit into one readable composition.
- Changing the date and time rotates the sky.
- Changing latitude and longitude changes the local perspective.
- The 3D view is interactive through orbit controls.
- The print preview is generated from the same calculated sky snapshot.
- Switching to Heliocentric keeps the same date/time but ignores location because the viewpoint is Sun-centered.
This is good for product validation and visual direction. For production-grade poster accuracy, the next engine step should use a larger verified star catalog and a backend astronomy library or service that handles time zones, precession, refraction, and high-precision ephemerides.
For the heliocentric view, the current approximation is based on JPL's lower-accuracy planet-position formulae and the 1800-2050 element table. That is enough for a strong product prototype, but a sellable astronomy print should eventually be checked against JPL Horizons or a production ephemeris.