Swiss Ephemeris binding for node.js
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Swiss Ephemeris binding for node.js.

See Swiss Ephemeris for more details.

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

Getting started

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.

Version 0.5.x Notes

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.


Getting julian day

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);

Getting Sun and Moon position


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.

Using ecliptic, equatorial or rectangular coordinates

On computing planet, star, node or apside positions, and using SEFLG_EQUATORIAL or SEFLG_XYZ in flag bits, name of the resulting property will be different from the case with ecliptic coordinates. Run examples/issue-23.js in details, please.

Ephemeris settings

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.