# Catalog provenance

Downloaded 2026-10-21 from the upstream D3-Celestial master data directory.
The GeoJSON catalogs retain upstream IDs and coordinates. The star-name file
is reduced to entries used by the magnitude-six catalog and name/desig/c fields.
The app implements its own renderer; it does not use the D3-Celestial renderer.

https://github.com/ofrohn/d3-celestial

The upstream project is BSD-3-Clause; its license is included here. Upstream
credits the following catalog sources in its README:

- Star catalog: Hipparcos, van Leeuwen (2007), VizieR I/311.
- Star designations and names: see the upstream README references [1b] and [1c].
- Messier objects: H. Frommert / SEDS, “Messier Objects with Data.”
- Constellation line patterns and label positions: IAU constellation pages,
  with conversions and modifications by Olaf Frohn. These are illustrative
  modern line patterns, not official IAU constellation boundaries.

All coordinates are J2000; GeoJSON longitude is right ascension expressed in
degrees on −180..180. This is converted to equatorial unit vectors by the app.

Retained originals, except the reduced star-name file:

- stars.6.json → web/data/stars.json
- starnames.json → web/data/starnames.json (filtered)
- constellations.lines.json → web/data/lines.json
- constellations.json → web/data/constellations.json
- messier.json → web/data/messier.json

Full upstream data-format reference: d3-celestial-data-sources.md.