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Swiss Ephemeris binding for node.js

Swiss Ephemeris binding for node.js

Swiss Ephemeris binding for node.js.

See Swiss Ephemeris for more details.

Supported platforms: Mac OS X | Windows | Linux | FreeBSD

To install run:

$ npm install swisseph

From version 0.5.x only nodejs 0.12 or newer supported.

To use with older nodejs version use swisseph 0.4.x or older.

From version 0.5.x only nodejs 0.12 supported, because of C addons API compatibility.

Also, project splited to swisseph and swisseph-api. swisseph responsible only for nodejs binding, but swisseph-api to access over the web.

var swisseph = require ('swisseph');
var date = {year: 2015, month: 1, day: 1, hour: 0};
var julday = swisseph.swe_julday (date.year, date.month,, date.hour, swisseph.SE_GREG_CAL);


var swisseph = require ('swisseph');
// Test date 
var date = {year: 2012, month: 1, day: 1, hour: 0};
console.log ('Test date:', date);
var flag = swisseph.SEFLG_SPEED;
// path to ephemeris data 
swisseph.swe_set_ephe_path (__dirname + '/../ephe');
// Julian day 
swisseph.swe_julday (date.year, date.month,, date.hour, swisseph.SE_GREG_CAL, function (julday_ut) {
    assert.equal (julday_ut, 2455927.5);
    console.log ('Julian UT day for date:', julday_ut);
    // Sun position 
    swisseph.swe_calc_ut (julday_ut, swisseph.SE_SUN, flag, function (body) {
        assert (!body.error, body.error);
        console.log ('Sun position:', body);
    // Moon position 
    swisseph.swe_calc_ut (julday_ut, swisseph.SE_MOON, flag, function (body) {
        assert (!body.error, body.error);
        console.log ('Moon position:', body);

For more examples see examples and test folders.

There are 3 different types of ephemeris supported:

  • Steve Moshier interpolation, covers 3000 BC – 3000 AD, preision 0.1 arcsec, no data files required.
  • Swiss Ephemeris is compressed version of DE431, covers 13000 BC - 17000 AD, precision 0.001 arcseconds, requires data files about 90MB. Download from
  • JPL NASA ephemeris is the state of the art ephemeris, DE431 covers 13000 BC - 17000 AD, maximum possible precision, requires data files 2.9GB. Download from

To use data files download them and put in folder then set path to the ephemeris folder by:

swisseph.swe_set_ephe_path ('/path/to/downloaded/ephemeris');

And select ephemeris by setting the flag:

// for Moshier 
body = swisseph.swe_calc_ut (julday_ut, swisseph.SE_SUN, swisseph.SEFLG_SPEED | swisseph.SEFLG_MOSEPH)
// for Swiss Ephemeris 
body = swisseph.swe_calc_ut (julday_ut, swisseph.SE_SUN, swisseph.SEFLG_SPEED | swisseph.SEFLG_SWIEPH)
// for JPL NASA ephemeris 
body = swisseph.swe_calc_ut (julday_ut, swisseph.SE_SUN, swisseph.SEFLG_SPEED | swisseph.SEFLG_JPLEPH)

To execute tests run from the root folder:

npm test

See Programming interface to the Swiss Ephemeris for more details.

This javascript programming interface is little different from the original api, basically for return values. For more details see src/*.h.

Please feel free to fill issues for bugs, erros and features.

The license for this project is the same as original Swiss Ephemeris.