Eclipse Tracker

Interactive solar eclipse map: eclipse.stanislas.cloud

Pick an eclipse (2023–2035), watch the Moon's shadow sweep across the Earth, and click anywhere to get local timings: contact times, coverage, totality duration, sun altitude — plus a cloud-cover forecast when the eclipse is close.

On load, the site answers the question that matters first: what will you see from where you are — using Cloudflare's coarse edge geolocation (city-level, no permission prompt, nothing stored). If your spot only gets a partial view, one click jumps you to the nearest point on the center line.

How it works

There is no database and no data files. A ~20-line Worker endpoint (/api/whereami) echoes the CDN's geolocation; everything else is computed in the browser from ephemerides with astronomy-engine:

                    Sun ☀
                     \
                      \  shadow axis (Sun → Moon center)
                   Moon ●
                      \ \
                 umbra \ \ penumbra
                        \ \
Earth ellipsoid ─────────▼──────────
                         E  ← axis ∩ WGS84 = shadow center

• Catalog — enumerate all solar eclipses 2023–2035 (SearchGlobalSolarEclipse).
• Path of totality — sample the eclipse around its peak; at each instant, intersect the Sun–Moon axis with the WGS84 ellipsoid, derive the umbra cone radius from similar triangles, offset perpendicular to the track, and re-project. Gives the center line and the north/south limits (src/lib/shadow.ts).
• Animated shadow — same math per animation frame: project the umbra/penumbra cone rim onto the ellipsoid and draw the footprint rings on the map.
• Local circumstances — SearchLocalSolarEclipse for the clicked point: C1–C4 contact times, obscuration, sun altitude. The sky simulation compares topocentric angular radii and separation of the two discs.
• Clouds — Open-Meteo hourly cloud cover, when the eclipse is within the 16-day forecast horizon.
• Distance to totality — great-circle distance from the selected point to the nearest sampled point of the center line.

The shadow math is validated in src/lib/shadow.test.ts against astronomy-engine's own greatest-eclipse predictions (< 0.5° difference). Overall accuracy is a few kilometers: great for a map, not for planning an expedition to the edge of the path.

Stack

• React + TypeScript + Vite, MapLibre GL with OpenFreeMap dark tiles
• Deployed as static assets on a Cloudflare Worker, auto-deployed from main by Workers Builds

Develop

bun install
bun run dev     # local dev server
bun run check   # typecheck + tests

Deploy

Pushes to main build and deploy automatically. Manual deploy: bun run deploy.

License

MIT