https://github.com/bluephlavio/eph

Represent, retrieve and manipulate ephemerides with python.
https://github.com/bluephlavio/eph

astronomy ephemeris jpl nasa solar-system

Last synced: about 2 months ago
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Represent, retrieve and manipulate ephemerides with python.

• Host: GitHub
• URL: https://github.com/bluephlavio/eph
• Owner: bluephlavio
• License: mit
• Created: 2017-02-26T11:24:07.000Z (almost 8 years ago)
• Default Branch: master
• Last Pushed: 2022-12-08T05:19:10.000Z (about 2 years ago)
• Last Synced: 2024-09-16T11:27:16.966Z (4 months ago)
• Topics: astronomy, ephemeris, jpl, nasa, solar-system
• Language: Python
• Homepage:
• Size: 515 KB
• Stars: 1
• Watchers: 0
• Forks: 2
• Open Issues: 6
• Metadata Files:
  • Readme: README.rst
  • Changelog: CHANGELOG
  • License: LICENSE

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README

        
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Readme

======

The ``eph`` package provides some useful functions, classes and tools

to *retrieve*, *parse* and *manipulate* ephemerides

in an `astropy `_-compatible way.

See `eph-howto`_ (jupyter notebook) for more info.

.. _eph-howto: https://nbviewer.jupyter.org/github/bluephlavio/edu/blob/master/eph-howto.ipynb

Basic Usage

-----------

.. code-block:: python

    import eph

    req = eph.JplReq() # create the request

    req.read('eph.ini', section='jplparams') # read parameters from 'jplparams' section in 'eph.ini'

    req.set({

        'COMMAND': 'venus',

        'START_TIME': '2007-11-17',

        'STOP_TIME': '2017-4-22'

        'STEP_SIZE': '10d'

        }) # set parameters from dictionary

    req['OBJ_DATA'] = False # set parameter dict-like

    req.csv = True # set parameter as attributes

    req.set(

        TABLE_TYPE='V',

        VEC_LABELS=False,

        VEC_TABLE=1

    ) # set position vectors output

    res = req.query() # perform the request obtaining a response from Jpl Horizons service

    e = res.parse() # parse the ephemeris in an astropy QTable

    from astropy.io import ascii

    ascii.write(e, format='csv') # write output data

The content of ``eph.ini`` can be something like this

(see ftp://ssd.jpl_process.nasa.gov/pub/ssd/horizons_batch_example.long

for a complete description of JPL parameters)

.. code-block:: ini

    [jplparams]

    MAKE_EPHEM=YES

    REFERENCE_PLANE=ECLIPTIC

    REF_SYSTEM=J2000

    OUT_UNITS=AU-D

Shortcuts

---------

``eph`` package defines also some useful shortcut functions to easily access Jpl Horizons data.

Instead of building a JplReq and get back a JplRes to parse, you can get an astropy QTable with

.. code-block:: python

    from eph import *

    from datetime import datetime

    e = get('venus', dates=['2000-1-1', datetime.now()])

Shortcut functions accept also one-date queries (non-interval) and multiple target objects.

Behind the scenes ``eph`` makes multiple calls to JPL Horizons system and merge the results in one

table. In this case non-key (used to join) columns are renamed with a prefix referring to the object

(e.g. column X for object venus becomes venus_X).

Meta info are listified and collapsed in a single value only if they take the same value for all objects.

.. code-block:: python

    from eph import *

    e = get(['venus', 'mars'], dates='2017-04-22')

Dates has datetime.now() as default value so it can be omitted if you want present data.

.. code-block:: python

    from eph import *

    e = get(['venus', 'mars'], table_type='V', vec_table=1) # present vector positional data for Venus and Mars

There are other shortcut functions like ``vec``, ``pos``, ``vel``, ``elem``, ``obs``, ``radec``, ``altaz``, etc.. to

simplify parameter settings.

For example, if you want vectors, type

.. code-block:: python

    e = vec('venus', dates=['2018-1-1', '2020-1-1']).

Command line tool

-----------------

``eph`` package also provides a command line tool:

.. code-block:: bash

    $ eph venus --dates 2007-11-07 2017-04-22

This command gives you an ephemeris table of Venus starting from 2007-11-17 to 2017-4-22.

You can also change the reference frame, the time-step size, the output etc..

through the options provided or setting up a config file. Check available options typing

.. code-block:: bash

    $ eph --help