@zodiacs/engine notice
========================

Astronomy Engine
----------------

The core runtime depends on astronomy-engine 2.1.19, Copyright (c) 2019-2023
Don Cross, distributed under the MIT License. Its distributed JavaScript source
retains the full MIT permission and warranty notice. Source and license metadata:
https://github.com/cosinekitty/astronomy

The package's frame module (src/frame.ts, built into the ephemeris chunk under
dist/) reproduces astronomy-engine's precession function, precession_rot, and
the calc entry's reduction module (src/calc-reduce.ts, built into
dist/calc.js) its function for an observer on the Earth's ellipsoid, terra:

  Copyright (c) 2019-2023 Don Cross <cosinekitty@gmail.com>
  MIT License: the permission and warranty notice is the one in this
  package's LICENSE file, word for word.

IAU 2000B nutation
------------------

The package's nutation module (src/nutation.ts, built into the same chunk)
carries the 77 luni-solar terms, fundamental arguments and fixed planetary
offsets of the IAU 2000B nutation model,

  D. D. McCarthy and B. J. Luzum 2003, An abridged model of the
  precession-nutation of the celestial pole. Celestial Mechanics and Dynamical
  Astronomy 85, 37-49; IERS Conventions (2003), chapter 5,

transcribed from the function iau2000b of the Naval Observatory Vector
Astrometry Software (NOVAS) C 3.1, nutation.c, as the package novas 3.1.1.5
distributes it (sha256
49d193c9e0d6dfb14650ed0b2603e3954ef02ab51f83d66869a769e892e471bb), a work of
the US Government, which its authors ask to be cited as:

  Barron, E. G., Kaplan, G. H., Bangert, J., Bartlett, J. L., Puatua, W.,
  Harris, W., & Barrett, P. (2011), "Naval Observatory Vector Astrometry
  Software (NOVAS) Version 3.1, Introducing a Python Edition," Bull. AAS, 43.

Its equation of the equinoxes adds two complementary terms from the IERS
Conventions (2010), table 5.2e (IERS, https://www.iers.org/).

Calculation entry
-----------------

The calc entry (dist/calc.js and the chunks it imports) carries the frame
bias of the IAU 2000 precession-nutation model, dpsi = -0.041775",
deps = -0.0068192" and dalpha0 = -0.0146", composed as

  G. Petit and B. Luzum (eds.) 2010, IERS Conventions (2010), IERS Technical
  Note No. 36, chapter 5, eq. 5.21,

composes it, and the obliquity of J2000.0 of the IAU 2006 precession,
84381.406", from

  N. Capitaine, P. T. Wallace and J. Chapront 2003, Expressions for IAU 2000
  precession quantities. Astronomy & Astrophysics 412, 567-586 (adopted by
  IAU 2006 Resolution B1).

Its bounds and its barycentre's error are measurements: the largest
differences of this package's own results from NASA JPL Horizons (DE441)
responses at 32 instants, and of astronomy-engine's barycentre from a
Newtonian barycentre and from Horizons's. They are not coefficients derived
from JPL data, and no JPL ephemeris value is in the package.

Essential dignities
-------------------

The techniques entry (dist/techniques.js) carries the tables of the
essential dignities as these works give them, and none of their text:

  Ptolemy, Tetrabiblos I.17-I.20, tr. F. E. Robbins (Loeb Classical Library,
  1940): domiciles, exaltations, the Egyptian terms.
  Dorotheus of Sidon, Carmen Astrologicum I.1-I.2, ed. and tr. D. Pingree
  (Leipzig: Teubner, 1976), pp. 161-162: domiciles, exaltations, triplicity
  lords.
  al-Biruni, The Book of Instruction in the Elements of the Art of Astrology
  (1029), tr. R. Ramsay Wright (London: Luzac, 1934), sections 440-453:
  detriments, triplicities, terms, the Chaldean faces.
  W. Lilly, Christian Astrology (London, 1647), p. 112: reception and the
  peregrine planet.

Rise, set and transit
---------------------

The sky entry (dist/sky.js) carries 34' of refraction at the horizon, from
the US Naval Observatory's Rise, Set, and Twilight Definitions
(https://aa.usno.navy.mil/faq/RST_defs, a work of the US Government); the
Moon's mean radius, 1,737.4 km, from

  B. A. Archinal et al. 2018, Report of the IAU Working Group on
  Cartographic Coordinates and Rotational Elements: 2015. Celestial
  Mechanics and Dynamical Astronomy 130:22;

the Sun's radius, 696,000 km, which subtends 959.64" at 1 au, where J.
Meeus, Astronomical Algorithms, 2nd ed. (Willmann-Bell, 1998), ch. 55, gives
959.63"; the astronomical unit, 149,597,870.7 km (IAU 2012 Resolution B2);
and the WGS84 ellipsoid, a = 6,378,137 m and 1/f = 298.257223563, from

  NIMA TR8350.2 2000, Department of Defense World Geodetic System 1984: Its
  Definition and Relationships with Local Geodetic Systems, 3rd ed.

ΔT (TT − UT1)
------------

The package's ΔT module, the model "zodiacs-deltat/1" that the package
exports as @zodiacs/engine/deltat, contains 32 values of Table S15, rounded
to 0.01 s, and constants of equations (4.1) and (5.1) from the work below.
The build places that module in a shared chunk under dist/, which
dist/deltat.js re-exports, so the values are in that chunk rather than in
dist/deltat.js itself.

  Stephenson, F. R., Morrison, L. V. & Hohenkerk, C. Y. 2016, Measurement of
  the Earth's rotation: 720 BC to AD 2015. Proc. R. Soc. A 472: 20160404.
  doi:10.1098/rspa.2016.0404
  Published under Creative Commons Attribution 4.0 International (CC BY 4.0):
  https://creativecommons.org/licenses/by/4.0/
  The values are used unmodified except for rounding; the engine rebuilds the
  authors' spline from them.

Its values from 1941 come from the United States Naval Observatory
(historic_deltat.data and tai-utc.dat, US Government works) and from the
International Earth Rotation and Reference Systems Service (IERS EOP 20 C04
and Bulletin A, finals2000A.all; IERS, https://www.iers.org/). They enter the
table as 91 values in 0.01 s.

GeoNames
--------

The optional @zodiacs/engine/geo client can read a compact index derived from
GeoNames cities15000, admin1CodesASCII, and countryInfo. GeoNames data is
licensed under Creative Commons Attribution 4.0 International (CC BY 4.0):

  https://www.geonames.org/
  https://creativecommons.org/licenses/by/4.0/

The Zodiacs.org index rounds latitude and longitude to two decimal places,
interns timezone, administrative-area, and country strings, sorts cities by
population, and shards records by the first folded ASCII letter. No GeoNames
records are bundled in this npm package: the country names in its Gregorian
adoption table come from tzdata (below). If you host, copy, or redistribute a
compatible GeoNames-derived index, retain this notice and attribution.

Time zone, leap-second and UT1 data
-----------------------------------

@zodiacs/engine/geo ships zone histories before 1970 compiled from the IANA
Time Zone Database 2025c with its backzone file (tzdata2025c.tar.gz, sha256
4aa79e4effee53fc4029ffe5f6ebe97937282ebcdf386d5d2da91ce84142f957), which is in
the public domain: https://www.iana.org/time-zones. From 1970 local time
comes from the host runtime's Intl/ICU data.

The core carries TAI - UTC from the IERS leap-second list, leap-seconds.list,
updated 2026-07-06 through IERS Bulletin C 72 and expiring 2027-06-28 (sha256
db5a895f16853b03bfc865e8d68f9fc8710ef1740e3400c701cd46a5bbbc3433), from the
IERS Earth Orientation Centre at Paris Observatory,
https://hpiers.obspm.fr/iers/bul/bulc/ntp/leap-seconds.list, whose header
states: "This file is in the public domain."

It carries UT1 - UTC for 1972 derived from the IERS EOP 20 C04 series,
eopc04.1962-now of 2026-09-28 (sha256
e16cfbba34574b8bad3cf81e2e56a84c2b4bbfd3c822cf9ebdd860bf97d711dc), from the
IERS Earth Orientation Centre at Paris Observatory,
https://hpiers.obspm.fr/iers/eop/eopc04/ (IERS, https://www.iers.org/), and
UT1 - UTC from 1973-01-02 from IERS finals2000A.all (Bulletin A) of
2026-09-24, from the IERS Rapid Service/Prediction Centre at the US Naval
Observatory, https://maia.usno.navy.mil/ (IERS, https://www.iers.org/).

The Earth Orientation Centre gives this technical note for the C04 series:

  Bizouard, C., Lambert, S., Gattano, C., Becker, O. & Richard, J.-Y. 2019,
  The IERS EOP 14C04 solution for Earth orientation parameters consistent
  with ITRF 2014. J. Geod. 93, 621-633. doi:10.1007/s00190-018-1186-3

Gregorian adoption dates
------------------------

@zodiacs/engine/geo carries a table of when 18 countries took the Gregorian
calendar (GREGORIAN_ADOPTION, in dist/geo.js). Its dates come from these
public-domain sources:

  IANA Time Zone Database 2025c, file calendars, which quotes H. Grotefend,
  Taschenbuch der Zeitrechnung des deutschen Mittelalters und der Neuzeit,
  ed. O. Grotefend (Hannover: Hahnsche Buchhandlung, 1941), pp. 26-28.
  H. Grotefend, Zeitrechnung des deutschen Mittelalters und der Neuzeit,
  vol. 1 (Hannover: Hahn, 1891), pp. 133-134.
  H. Grotefend, Taschenbuch der Zeitrechnung des deutschen Mittelalters und
  der Neuzeit (Hannover and Leipzig: Hahn, 1898), pp. 23-24.

Its country names come from the IANA Time Zone Database 2025c, file
iso3166.tab, which is in the public domain.

Star positions and motions
--------------------------

@zodiacs/engine/vedic and @zodiacs/engine/calc carry 22 published values for
the objects of four star-based ayanamsas, in a shared chunk under dist/ that
dist/vedic.js and dist/calc.js import. Twenty of them were obtained through
the VizieR catalogue access tool (DOI 10.26093/cds/vizier) and the SIMBAD
database (M. Wenger et al. 2000, A&AS 143, 9) of the CDS, Strasbourg
Astronomical Observatory, France:

  F. van Leeuwen 2007, A&A 474, 653 (VizieR I/311, Hipparcos, the New
  Reduction): the positions, proper motions and parallaxes of Spica,
  zeta Psc A and delta Cnc.
  G. A. Gontcharov 2006, Astronomy Letters 32, 759 (VizieR III/252, Pulkovo
  radial velocities): the radial velocity of zeta Psc A.
  B. Famaey et al. 2005, A&A 430, 165 (VizieR J/A+A/430/165,
  DOI 10.26093/cds/vizier.34300165): the radial velocity of delta Cnc.
  SIMBAD: the radial velocity of Spica, and the ICRS position of Sgr A*
  (L. Petrov et al. 2011).

The other two, the proper motion of Sgr A*, come from M. J. Reid and
A. Brunthaler 2004, ApJ 616, 872, table 2. LICENSING.md gives the terms.
