Positions of fixed stars

Almanac 0.3.0 adds the altitude and azimuth of any fixed star in TypeScript and Swift.

• starAltAz(raDeg:decDeg:at:observer:) / starAltAz(raDeg, decDeg, time, observer) takes a star's J2000 catalog right ascension and declination and returns its refracted topocentric altitude and azimuth. It precesses and nutates the position to date and uses the same sidereal time and refraction as sunAltAz and moonAltAz.
• Annual aberration, proper motion, and stellar parallax are not applied. Aberration is at most 20.5″, and all but a few fast-moving stars shift by only arcseconds per decade.
• An out-of-range right ascension or declination is a validation error, like an invalid observer.
• The library ships no star catalog; callers pass the coordinates they already carry.

The star positions are checked against the USNO celestial-navigation almanac for the navigational stars at Victoria and at 35°S, on the 2026 equinoxes and solstices, 1999-01-17, and 2050-06-21, with J2000 positions from SIMBAD. The tests compare every star above 10° altitude and leave out the twelve stars whose proper motion would exceed the tolerance by 2050.

Positions checked	Worst altitude error	Worst azimuth error	Tolerance
197	0.45′	0.51′	1′

Validation includes 88 TypeScript tests, 93 Swift release tests, and the shared fixture and parity checks.

npm install @openwaters/almanac@0.3.0

.package(url: "https://github.com/openwatersio/almanac.git", exact: "0.3.0")

Requested in #12. Changes: #13, #14.

Full changelog.