NATARAJACelestial sphere and coordinate frames
Learning outcomes & permitted supports
- Fix your observer on Earth first, then place zenith, nadir, poles, equator and horizons on YOUR sphere.
- Predict pole altitude (= latitude), diurnal paths and rising/setting for any latitude and declination.
- Convert (declination, LHA) ↔ (altitude, azimuth) and explain why alt/az are observer-local.
Supports in this lab: four synchronized views (3D inside/outside cameras + 2D dome + side elevation) of one engine-computed geometry; readout mirrors everything.
Glossary: celestial sphere · zenith · nadir · celestial horizon · celestial poles · celestial equator · declination · LHA · altitude · azimuth · diurnal circle · circumpolar · zenith distance
Step 1 — you, on the Earth
Everything below is your sky, built from this position. Latitude sets the whole geometry (pole height, tilt of every star's path). Longitude decides which bodies are up right now — it enters through the hour angle: LHA = GHA + east longitude.
Step 2 — your celestial sphere, in 3D
Loading 3D sphere…
Drag (or arrow keys) to orbit the whole sphere — zenith, nadir, poles, equator, meridian and the azimuth arc all labelled.
Same sky — 2D dome (looking up)
Same sky — 2D side elevation (textbook)
The body & the clock
The four classics: latitude 0 → stars rise vertically; slide poleward → the same stars circle without rising; set dec = lat → the body threads your zenith; play at LHA 315° and follow one full diurnal circle through all four views at once.
Engine readout
| Altitude | 46° 26.6′ |
|---|---|
| Azimuth (true) | 090° 54.2′ |
| Elevated pole | N pole at 18° 56.4′ — always = your latitude |
| Diurnal behaviour | rises and sets |
| Meridian altitude | 84° 03.6′ bearing S |
| Rises at azimuth | 076° 14.5′ |