D3-Celestial by Olaf Frohn (BSD-3-Clause)
https://github.com/ofrohn/d3-celestial
Pinned source: 7e720a3de062059d4c5400a379146a601d9010e0 (retrieved 2026-09-17)
License: LICENSE (same directory)

Uses Celestial.projection and D3's spherical path clipping, with a custom,
non-interactive Canvas renderer for the twelve Beijing monthly views.
Data subset: stars.6.json (Hipparcos/XHIP) with magnitude <=4.0;
starnames.json (Chinese names); constellations.json and constellations.lines.json.
monthly-catalog.json mechanically retains source coordinates, magnitude and
line geometry, drops unused languages and simplifies selected Chinese glyphs.
Data format documentation: DATA-SOURCES.md.
Upstream source acknowledgements:
XHIP, Anderson & Francis (2012), VizieR V/137D;
star-name translations from Stellarium skycultures;
IAU constellation data, label positions/line modifications by Olaf Frohn;
translated constellation names from Wikipedia's multilingual constellation list.
https://github.com/ofrohn/d3-celestial/blob/7e720a3de062059d4c5400a379146a601d9010e0/readme.md#files
Original data and build script are retained in the source checkout.

D3 v3.5.17, Copyright Mike Bostock, BSD-3-Clause: D3-LICENSE.
Astronomy Engine by Don Cross, MIT: /astronomy-LICENSE.txt.
Star positions are precessed/nutated from J2000 to the selected date;
proper motion, refraction, local terrain, cloud and light pollution are not modeled.
Milky Way contours: Jose R. Vieira, Milky Way Outline Catalog,
https://www.skymap.com/milkyway_cat.htm, via the pinned D3-Celestial mw.json.
Contour winding is normalized per polygon before spherical rendering.
Ecliptic is the true ecliptic of date, transformed by Astronomy Engine;
equator is the equator of date. Dashed lines are coordinate guides.
Beijing static-v1 contains 12 reusable monthly stellar reference views in
desktop/mobile sizes, computed offline at each month's day 15, 21:00 in 2026.
These illustrative charts omit moving Solar System bodies and are not intended
for precision pointing; the browser loads the month URL directly, without a
manifest, date-dependent calculation, or star-chart API request.
Custom places use their IANA timezone, including the selected month's DST.
The renderer is shared between pre-generation and custom-place calculations.
Geometric horizon, Beijing 39.9042N 116.4074E, day 15 at 21:00 UTC+08:00.
Rendered entirely from self-hosted scripts and catalogs; no remote map iframe.