StormTrak Sky: celestial data, calculations and illustration credits

Stars: HYG 4.2, David Nash / Astronomy Nexus, based on the Hipparcos,
Yale Bright Star and Gliese catalogues.
https://www.astronexus.com/projects/hyg
https://www.astronexus.com/projects/hyg-details
License: Creative Commons Attribution-ShareAlike 4.0 International
https://creativecommons.org/licenses/by-sa/4.0/
Full license: /assets/sky/CC-BY-SA-4.0.txt

StormTrak modifications: selected 1,288 HIP-identified stars at apparent
magnitude <= 4.8, plus Eta Ursae Minoris (4.95) to complete the Little Dipper;
selected positional, motion, brightness and color-index columns; sorted by
apparent magnitude. The modified data subset is distributed under CC BY-SA 4.0:
/assets/sky/sky-bright-stars.json
Computed star directions retain this source and license.
Static demonstration and preview star directions in sky-demo-celestial.json
(bundled into sky-runtime.js) retain the same source and CC BY-SA 4.0 license.
The source catalogue and computed directions are not a claim of actual
visibility through local clouds, haze, trees or light pollution.

Sun/Moon positions: existing StormTrak Meeus/NOAA and perturbed lunar orbit
calculations. Planets and coordinate transforms: Astronomy Engine 2.1.19,
Copyright (c) 2019-2023 Don Cross, MIT License.
https://github.com/cosinekitty/astronomy/tree/v2.1.19
Full license: /assets/sky/ASTRONOMY-ENGINE-LICENSE.txt

Constellation HUD patterns: original simplified StormTrak line choices between
catalogue stars, not IAU boundary maps. No Stellarium artwork was used.
The IAU defines constellation regions, not mandatory connecting-line patterns:
https://iauarchive.eso.org/public/themes/constellations/

Milky Way: original procedural glow around the calculated galactic equator.
The orientation is astronomical; the brightness and texture are illustrative.
No ESA/Gaia sky photograph or third-party Milky Way texture is included.

All directions are geometric (airless), relative to true north and a level,
sea-level horizon. Luminosity, halos, disk sizes and atmospheric movement are
stylized for a small display. Stars have catalogue proper motion; small annual
parallax/aberration and observed atmospheric refraction are not simulated.
Twilight and moonlight govern visibility, with cloud/fog/weather attenuation.

Independent planet checks: NASA/JPL Horizons observer ephemerides.
https://ssd.jpl.nasa.gov/horizons/manual.html

Twilight definitions: U.S. Naval Observatory.
https://aa.usno.navy.mil/faq/RST_defs
Moonlight and Milky Way visibility: NASA Night Sky Network.
https://nightsky.jpl.nasa.gov/news/29/