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2.10.3-2 • 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 programmer's 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.


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.


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.


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 https://www.astro.com/ftp/swisseph/ephe/ 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 inaccuracy or bug in this library, or if you find an upstream update that is not yet included in this library, feel free to open an issue or a pull request.


  • While worker_threads are supported, the underlying C library is single threaded and contains process-wide settings. Functions such as set_ephe_path() or set_sid_mode() will affect the entire process, including all worker_threads. While you can still use worker_threads as long as you don't change settings from other threads in the middle of calculations, true thread-safe multithreading can only be achieved using child_process.

  • This library is a C/C++ add-on designed for Node.JS only, it will not work in browsers, other JS engines or in any other environment that does not support native C/C++ add-ons. In order to install this library, the target system must have the necessary build tools installed, such as python, make and gcc on Linux, xcode on Mac, visual c++ on Windows, and/or other equivalent solutions.


Copyright © 2021-2022, Timotej Valentin Rojko


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