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Star Sequencer
Your real night sky, turned into music — a scan line sweeps the stars above you and plays what it finds
Sky Projection
The sequencer uses the HYG star catalog — 1,616 real stars pre-filtered to magnitude < 5 (naked-eye visible) — and projects them onto your screen using client-side positional astronomy.
Browser geolocation returns your latitude and longitude. Falls back to NYC if denied.
Current Date → Julian Date → Greenwich Mean Sidereal Time → Local Sidereal Time for your longitude.
For each star: Right Ascension / Declination + LST + latitude → Hour Angle → altitude and azimuth (horizon coordinates).
Stars below the horizon are filtered out. Azimuth maps to X, altitude maps to Y — zenith at top, horizon at bottom.
The projection recalculates every 60 seconds to account for Earth's rotation. Constellations rise and set in real time.
Audio Mapping
When the scan line crosses a star, its physical properties determine the sound. Every parameter maps to a real astronomical measurement.
Altitude (0°–90°) maps to a selectable musical scale across 2 octaves (C3–C5). Stars near the zenith produce the highest notes, stars near the horizon the lowest. Default is pentatonic — choose chromatic, major, minor, or whole tone in the synth panel.
Apparent magnitude → gain. Sirius (mag -1.44) plays at full volume. A dim mag-5 star is barely audible. The mapping is linear: brighter star = louder note.
Star color index (B-V value) determines oscillator type by default. Blue-white stars (Rigel, B-V ≈ -0.03) produce pure sine waves. Yellow stars (Sun-like, B-V ≈ 0.65) use warmer triangle waves. Override in the synth panel.
Configurable attack (5ms–500ms) and decay (0.1s–3.0s). Default is a quick 20ms onset with 0.8s exponential decay — bell-like and ambient. The delay effect adds echo with feedback for spatial depth.
Clicking a zodiac constellation plays all its visible stars simultaneously, sorted by altitude with 80ms stagger — creating a rising arpeggio whose shape mirrors the constellation's geometry in the sky.
Playback
The scan line sweeps across the star field at a configurable speed. Playback state — speed, position, play/pause — is tracked using wall-clock timestamps so the animation stays smooth regardless of frame rate.
The scan position is derived from (Date.now() - startTimestamp) * speed on every frame — no integration drift, no per-frame timer churn. Stars are projected from your browser's geolocation, so the composition is specific to your place and moment.
Stack
1,616 pre-filtered stars with RA/Dec, magnitude, color index, constellation, and proper names.
Julian Date → GMST → LST, then equatorial to horizon coordinate conversion for any location on Earth.
60fps rendering with radial gradients for glow, proximity brightening, hit flashes, scan line bloom, and zodiac overlays.
Real-time oscillator synthesis with configurable waveform, envelope, detune, and delay feedback loop.
Timestamp-based playback tracking for frame-rate independent scan line animation.
Browser location for real-sky projection. Reprojects every 60s for Earth rotation.