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https://github.com/onekiloparsec/aa-js
The most comprehensive collection of accurate astronomical algorithms in JavaScript (TypeScript).
https://github.com/onekiloparsec/aa-js
astronomy astronomy-astrophysics astronomy-library astronomy-software coordinates-transformations moon planets sun transit
Last synced: 13 days ago
JSON representation
The most comprehensive collection of accurate astronomical algorithms in JavaScript (TypeScript).
- Host: GitHub
- URL: https://github.com/onekiloparsec/aa-js
- Owner: onekiloparsec
- License: mit
- Created: 2018-02-18T12:13:07.000Z (over 6 years ago)
- Default Branch: master
- Last Pushed: 2024-09-30T19:38:11.000Z (about 1 month ago)
- Last Synced: 2024-10-08T16:07:56.913Z (about 1 month ago)
- Topics: astronomy, astronomy-astrophysics, astronomy-library, astronomy-software, coordinates-transformations, moon, planets, sun, transit
- Language: TypeScript
- Homepage: https://onekiloparsec.dev/aa-js/
- Size: 2.84 MB
- Stars: 41
- Watchers: 6
- Forks: 5
- Open Issues: 8
-
Metadata Files:
- Readme: README.md
- Funding: .github/FUNDING.yml
- License: LICENSE
Awesome Lists containing this project
README
aa-js
============
 [](https://codecov.io/gh/onekiloparsec/aa-js)
The most comprehensive collection of accurate astronomical algorithms (AA) in JavaScript (TypeScript).
The v3 offered arbitrary-precision computations, thanks to [decimal.js](https://github.com/MikeMcl/decimal.js).
But it was thousands (if not millions) of times slower than the original implementation, making its usage in a browser
very difficult. After some nightly hours to optimise it and having most of both implementations side-by-side, we decided
to remove decimal.js entirely.
Other AA
implementations: [Swift (SwiftAA)](https://github.com/onekiloparsec/SwiftAA), [C# (AASharp)](https://github.com/jsauve/AASharp).
At the beginning, `aa-js` is the port in javascript of the C++ implementation of Astronomical
Algorithms by J.P. Naughter, called [AA+](http://www.naughter.com/aa.html),
based on the reference text book by Jean Meeus. It is written in TypeScript, and
covered as much as possible with tests validating the correctness
of the algorithms. Tests are inspired from Jean Meeus' book and those written in
SwiftAA, and are much more extended than what is available
in AA+.
`aa-js` is the backbone of scientific algorithms used
in [Arcsecond.io](https://www.arcsecond.io).
Main Changes in V4
================
No big API changes, except there are no more Decimal.js at all, and thus no `highPrecision` parameter. The method
signatures have not changed, but all return types are based on `number`.
Small changes:
- The return type of `getJulianDay` is now always `JulianDay` and not `JulianDay | undefined`. If really the build of a
JD is not correct, `J2000` is returned with a warning.
Main Changes in V3
================
- ~~All algorithms based on arbitrary-precision operations thanks
to [decimal.js](https://github.com/MikeMcl/decimal.js).~~
- **BREAKING** (since v3.2) Equatorial coordinates uses right ascension expressed in `Degree` not `Hour`.
- **BREAKING** (since v3.2) Input parameters of the `coordinates` modules now use complete coordinates objects, rather
than individual members to reduce the number of parameters in the functions.
- ~~**BREAKING** (since v3.4) The precision of Decimal.js is not set to a default value. It is left to the consumer.~~
- Moved all (non-Earth) planets modules inside a `planets` folder.
- **Addition of numerous orbital getters for planets** (mean longitude, semi-major axis, inclination, eccentricity...)
- Much easier and cleaner distinction between *heliocentric* and *geocentric* coordinates of planets.
- Added easy accessor for apparent geocentric equatorial coordinates of planets.
- Added a transformation from equatorial to *topocentric* coordinates.
- Important bugfix on `getPositionAngle` and `getPhaseAngle` in the `Moon` module.
- Added easy accessors for rise, transit and set times for every planet.
- Numerous bugfixes, and added methods for dates, julian days
Available Modules
================
* Planets: all the (static and dynamic) details, coordinates, quantities about
`Mercury`, `Venus`, `Mars`, `Jupiter`, `Saturn`, `Neptune` and of course `Pluto`: planet constants, aphelion,
perihelion, phase angle, illuminated fraction, magnitude, semi-diameters, heliocentric & geocentric coordinates,
distance from earth, velocities, orbital details etc.
* In addition, for `Mars`: the planetocentric declination of the Sun and the
Earth.
* In addition, for `Jupiter`: the planetocentric declination of the Sun and the
Earth.
* In addition, for `Saturn`: the details of the rings system.
* `Sun`: mean & true anomaly, coordinates.
* `Earth`: all the coordinates, mean anomaly, radius vector (distance) etc.
* Inside `Earth` module: `nutation`: in longitude, for obliquity, true & mean obliquity of the ecliptic.
* Inside `Earth` module: `aberration`: ecliptic and equatorial.
* `Earth.Moon`: phases, age, apparent coordinates etc.
* `juliandays`: creation, transformation, local mean sidereal time.
* `times`: transformation between UTC, TT, AI, UT1...
* `cosmology`: the cosmology calculator from Ned Wright's, but re-implemented, and tested.
* `distances`: all the conversions of small and extra-galactic distances.
* `coordinates`: all computation of parallactic angle, great circle angle, precessions, transformations (equatorial to
ecliptic, galactic, topocentric, and inverse etc.).
* `sexagesimal`: utilities for transforming values between decimal and sexagesimal.
* `risetransitset`: get rise, transit and set hours, dates, julian days, as well
as altitude.
* `exoplanets`: **WIP** module to hold exoplanet transit details calculations.
as altitude.
Installation
================
`npm install aa-js`
Usage
================
```
import { juliandays, Earth } from 'aa-js'
const jd = juliandays.getJulianDay(new Date())
const coords = Earth.Moon.getEquatorialCoordinates(jd)
```
Documentation
================
Almost every method is documented (quite sparingly
sometimes). A good knowledge of basic astronomy helps very much.
A copy of the Astronomical Algorithms textbook, by Jean Meeus
([amazon](https://www.amazon.fr/Astronomical-Algorithms-J-Meeus/dp/0943396352/ref=sr_1_6?qid=1654447735&refinements=p_27%3AJean+Meeus&s=books&sr=1-6))
would also help, since many methods refer to it.
The documentation is published in [onekiloparsec.dev/aa-js](https://onekiloparsec.dev/aa-js).
Benchmarks
================
To run benchmarks, install `vite-node` globally (`npm i -g vite-node`), then run
individual benchmark like this:
```bash
npx vite-node benchmark/planets/jupiter/apparent-equatorial-coordinates.js
```