swiss-ephemeris

Haskell bindings for the Swiss Ephemeris library.

See the tests in the spec folder for example usage, but here's a simple "main" that demonstrates the current abilities, inspired by the sample program in the official library:

import SwissEphemeris

main :: IO
main = do 
  -- location of your ephemeris directory, must be absolute. We bundle a sample one in `swedist`.
  setEphemeridesPath "/Users/luis/code/swiss-ephemeris/swedist/sweph_18"

  let time = julianDay 1989 1 6 0.0
  let place = defaultCoords{lat = 14.0839053, lng = -87.2750137}
  -- locate all bodies between the Sun and Chiron (further asteroids currently not supported, but they're an enum entry away)
  let planetPositions = map (\p -> (p, (calculateCoordinates time p))) [Sun .. Chiron]
  -- use the Placidus house system, which is the most traditional.
  let cusps  = calculateCusps time place Placidus

  forM_ planetPositions $ \(planet, coord)->
    putStrLn $ show planet <> ": " <> show coord
  putStrLn $ "Cusps: " <> show cusps

Should print the latitude and longitude (plus some velocities) for all planets, and the cusps and other major angles.

To see actual results, check out the tests. For some more advanced examples, see swetest.c and swemini.c in the csrc directory: they're the test/example programs provided by the original authors.

Notes

All the code in the csrc folder comes directly from the latest official tarball, v2.09.01.

The swedist folder includes the original documentation from the tarball in PDF (see the doc) folder, and a copy of ephemeris data files.

For other formats of the original documentation, see: https://www.astro.com/ftp/swisseph/doc/

The authors also host HTML versions of the manuals. Two are provided, a general reference and a programming reference. Both are very useful to get acquainted with the functionality and implementation details.

• General Reference
• Programmer's Reference

Ephemerides files

As noted in the original documentation you can omit the setEphePath call and calculations will use a built-in analytical ephemeris which:

provides "only" a precision of 0.1 arc seconds for the planets and 3" for the Moon. No asteroids will be available, and no barycentric option can be used.

For convenience, we bundle a few files for the time range 1800 AD – 2399 AD. If you were born before that, or plan to code e.g. transits for after that (!) or you'd prefer even more precision, you can download more ephemerides files from the astro.com downloads page

I chose the bundled files due to this comment in the official docs:

If the [JPL] file is too big, then you can download the files sepl_18.se1 and semo_18.se1 from here: http://www.astro.com/ftp/swisseph/ephe/

For a full explanation of the files available, see the Description of the Ephemerides section of the original manual, also of interest is the comparison between the Swiss Ephemeris and the raw NASA JPL data.

CI Build

You'll notice that I build against Github's macos-latest VM. This mirrors my development machine -- I noticed that the tests suffer a precision degradation when run on ubuntu, e.g.:

 expected: Right (Coordinates {lng = 285.64724200024165, lat = -8.254238068673002e-5, distance = 0.983344884137739, lngSpeed = 1.0196526213625938, latSpeed = 1.4968387810319695e-5, distSpeed = 1.734078975098347e-5})
  but got: Right (Coordinates {lng = 285.6472420002416, lat = -8.254238068996486e-5, distance = 0.9833448841377388, lngSpeed = 1.0196526213625938, latSpeed = 1.496838781028185e-5, distSpeed = 1.7340789750982604e-5})

Not sure if it's due to the C compiler in the GH environment, or if it's something on the actual software; however, caveat emptor!

Contributing

I've only made available the types and functions that are useful for my own, traditional, horoscope calculations. Feel free to add more! See the astro.com documentation for ideas.