An interactive astronomy engine — built for everyone.
Drive the celestial sphere through deep time. Watch the analemma trace itself, follow a gnomon's shadow across solstice arcs, or step outside the sky to see the whole framework at once.
Scenes
Each scene is a bookmarkable URL — drop straight into the right view.
Real stars, constellation lines and boundaries, asterisms, deep-sky objects, and the Milky Way — drawn on a clean horizon.
Open scene →The Sun's diurnal arc at solstices and equinox, with meridian, celestial equator, ecliptic, and today's path overlaid.
Open scene →A gnomon (śaṅku) on the ground, casting its real shadow as the Sun moves. Zodiac boundaries laid as arcs on the floor.
Open scene →The 27 nakshatras laid out along the sidereal ecliptic, with the live Sun–Moon tithi arc highlighted.
Open scene →The Sun, Moon, and five classical planets tracked on the real ephemeris, framed by the celestial and ecliptic poles and reference lines.
Open scene →A photographic, textured Milky Way wrapped across the sky — find the galactic centre and trace the band with the naked eye.
Open scene →The horoscope frame — the ascendant (lagna) and midheaven marked on the zodiac band, with the meridian and celestial equator for reference.
Open scene →Astrolabe · यन्त्रराज
A classical stereographic projection — the north celestial pole sits at the centre, declination circles grow outward, and the brass rim lands on the Tropic of Capricorn. Spin time forward and the disk rotates like a real planisphere.
Viewing modes
The same simulation reshapes itself for the screen in front of you.
Standard 60–90° perspective camera, anchored at the observer, looking outward. The everyday view on a laptop or monitor.
Step outside the celestial sphere and watch the whole grid framework rotate from afar. Useful for teaching the geometry itself.
A classical stereographic projection onto a brass disk — the north pole at centre, declination circles growing outward. Speed up time and it spins like a real planisphere.
Stand inside the celestial sphere in stereoscopic WebXR — any browser-capable headset (Quest, Vive, Index) connects with one tap. No install.
Engine
The simulation primitives the scenes are composed from — all exposed in the operator console.
Dynamically resolves the precession of the equinoxes — shift cleanly between tropical and sidereal frames across deep time.
Adjustable wireframe sky with concentric altitude rings and azimuth meridians converging at the zenith. Customizable spacing.
From microsecond steps to cosmic timescales — same engine, same precision. Pause, scale, or lock the clock to a fixed time of day.
Sun, Moon, and the five classical planets — visible bodies tracked on the actual ephemeris, with per-body scale and labels.
A separate dark-mode control surface that runs on a phone or tablet over the local network — wireless, hands-free presentation.
Narrated tours that play themselves — walk the analemma, swing the full-moon along the horizon, or step through a lunar year of nakshatras. Each line is human-readable.
Search any star, planet, constellation, asterism, or nakshatra — read its facts, draw its day's path, or aim the camera (and your headset) straight at it.
Speak or type plain-language commands — “show the ecliptic”, “jump to next full moon”, “view orbit”. A built-in cheatsheet lists every toggle.
Run it anywhere
The same code powers the web app and the offline Windows build. Pick the surface that fits.