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    2.10.2-2 • Public • Published


    The definitive Swiss Ephemeris bindings for Node.js
    Everything you need to create Astrology and Astronomy applications with javascript and node

    • 100% API coverage
    • Built-in Typescript declarations and ESM exports
    • Built-in intellisense documentation
    • Version matched
    • Made with the N-API

    Official programmers documentation for the Swiss Ephemeris by Astrodienst AG
    Official guide for the Swiss Ephemeris by Astrodienst AG
    Sweph on Github
    Sweph on NPM

    Installation and Licensing

    This library follows the licensing requirements for the Swiss Ephemeris by Astrodienst AG.

    - GPL

    Up to and including version 2.10.0, this library is licensed under GPL-2.0.
    To install and use this library under GPL, use npm install sweph@gpl or npm install sweph@2.10.0.

    - AGPL

    Starting from version 2.10.1 and later, this library is licensed under AGPL-3.0.
    To install and use the latest version of this library under AGPL, use npm install sweph or npm install sweph@latest.

    - LGPL

    If you own a professional license for the Swiss Ephemeris, you may use any version of this library under LGPL-3.0.


    This library is version locked to the Swiss Ephemeris in addition to its own revisions. For example, version 2.10.1-1 corresponds to the Swiss Ephemeris version 2.10.1 and this library's revision 1.

    Updates to this library will be released under new revisions, while updates to Swiss Ephemeris will be released under matching semver versions.


    This library is fully typed and documented via intellisense. To access its documentation simply hover over its functions in your favorite code editor:


    Ephemeris files

    This library does not include any ephemeris files. To use the Swiss Ephemeris files, download them from and call set_ephe_path() to point the library to the folder containing the ephemeris files.

    Each main ephemeris file covers a range of 600 years starting from the century indicated in its name, for example the file sepl_18.se1 is valid from year 1800 until year 2400. The following files are available:

    • sepl files - planets (AD)
    • seplm files - planets (BC)
    • semo files - moon (AD)
    • semom files - moon (BC)
    • seas files - main asteroids (AD)
    • seasm files - main asteroids (BC)

    For advanced usage, the following files can also be found:

    • astxxx folders - files for individual asteroids (600 years)
    • longfiles folder - files for individual asteroids (6000 years)
    • jplfiles folder - files for nasa's jpl ephemerides
    • sat folder - files for planetary moons

    More information can be found in the Swiss Ephemeris files documentation.


    If you find any innacuracy or bug in this library, or if you find an update that is not yet included in this library, feel free to open an issue or a pull request.

    Known Issues and Caveats

    • Due to how the underlying C library operates, you may find that the error field returned by some functions will contain random data even if there is no actual error. This can happen when existing memory buffers are recycled therefore the user must always check the returned flag values as per the Swiss Ephemeris documentation.
    • While worker_threads are supported, the underlying C library is single threaded and its settings are global. Functions such as set_ephe_path() will affect the entire process, including worker_threads. While you can still use worker_threads as long as you dont change settings from other threads in the middle of calculations, true thread-safe multithreading can be achieved using child_process instead.


    Copyright © 2021, Timotej Valentin Rojko


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