PyMeeus

Library of astronomical algorithms in Python.

PyMeeus is a Python implementation of the astronomical algorithms
described in the classical book 'Astronomical Algorithms, 2nd Edition,
Willmann-Bell Inc. (1998)' by Jean Meeus.

There are great astronomical libraries out there. For instance, if
you're looking for high precision and speed you should take a look at
libnova <http://libnova.sourceforge.net/>. For a set of python
modules aimed at professional astronomers, you should look at
Astropy <http://www.astropy.org/>. On the other hand, the advantages
of PyMeeus are its simplicity, ease of use, ease of reading, ease of
installation (it has the minimum amount of dependencies) and abundant
documentation.

Installation

The easiest way of installing PyMeeus is using pip:

.. code:: sh

pip install pymeeus

Or, for a per-user installation:

.. code:: sh

pip install --user pymeeus

If you prefer Python3, you can use:

.. code:: sh

pip3 install --user pymeeus

If you have PyMeeus already installed, but want to upgrade to the latest
version:

.. code:: sh

pip3 install -U pymeeus

Properly Using PyMeeus

It is very common to try to run PyMeeus like this:

.. code:: sh

import pymeeus

mydate = pymeeus.Epoch(1992, 10, 13.0)

But if you do that, you'll get an error like this:

.. code:: sh

Traceback (most recent call last):
File "/home/user/test/test.py", line 3, in
epoch = pymeeus.Epoch(1992, 10, 13.0)
AttributeError: module 'pymeeus' has no attribute 'Epoch'

This issue points to a misunderstanding that is very common in the
Python world. The keyword import is used to import MODULES\ ...
but PyMeeus is NOT a module: It is a LIBRARY composed of
MULTIPLE modules (Angle, Epoch, Coordinates, etc). As of
today, the library Pymeeus has 19 different modules (if you look into
the directory where pip stores the library, you'll find one ".py"
file per module).

Therefore if you want to use, for example, the module Angle you
should use:

.. code:: sh

import pymeeus.Angle

I.e., your module is pymeeus.Angle, and not just Angle.

But there is more! When you use import to fetch a module, you must
then use the dot notation to access the components of the module
(classes, functions, etc). For instance:

.. code:: sh

import pymeeus.Angle

i = pymeeus.Angle.Angle(11.94524)

In this case, you are telling the Python interpreter that you want to
use the class Angle (with parameter '11.94524') from the module
Angle belonging to the library pymeeus.

There is, however, a more practical (and common) way to handle modules
using the statement from <MODULE> import <COMPONENT>. For instance:

.. code:: sh

from pymeeus.Angle import Angle
from pymeeus.Epoch import Epoch, JDE2000
from math import sin, cos, tan, acos, atan2, sqrt, radians, log10

This way is preferred because, among other reasons, only the required
components are loaded into memory instead of the whole module. Also, now
the component is directly added to your execution environment, which
means that you no longer need to use the dot notation.

Therefore, the script at the beginning would become:

.. code:: sh

from pymeeus.Epoch import Epoch

mydate = Epoch(1992, 10, 13.0)

Meta

Author: Dagoberto Salazar

Distributed under the GNU Lesser General Public License v3 (LGPLv3). See
LICENSE.txt and COPYING.LESSER for more information.

Documentation: https://pymeeus.readthedocs.io/en/latest/

GitHub: https://github.com/architest/pymeeus

If you have Sphinx installed, you can generate your own, latest
documentation going to directory 'docs' and issuing:

.. code:: sh

make html

Then the HTML documentation pages can be found in 'build/html'.

Contributing

The preferred method to contribute is through forking and pull requests:

Fork it (https://github.com/architest/pymeeus/fork)
Create your feature branch (git checkout -b feature/fooBar)
Commit your changes (git commit -am 'Add some fooBar')
Push to the branch (git push origin feature/fooBar)
Create a new Pull Request

Please bear in mind that PyMeeus follows the PEP8 style guide for Python
code (PEP8) <https://www.python.org/dev/peps/pep-0008/?>. We suggest
you install and use a linter like
Flake8 <http://flake8.pycqa.org/en/latest/> before contributing.

Additionally, PyMeeus makes heavy use of automatic tests. As a general
rule, every function or method added must have a corresponding test in
the proper place in tests directory.

Finally, documentation is also a big thing here. Add proper and abundant
documentation to your new code. This also includes in-line comments!!!.

Contributors

Neil Freeman <https://github.com/fitnr>__ - Fixed undefined
variable in Epoch.tt2ut
molsen234 <https://github.com/molsen234>__ - Fixed bug when using
fractional seconds, minutes, hours or days
Sebastian Veigl <https://github.com/sebastian1306>__ - Added
functionality for Jupiter's moons
Sophie Scholz - Added functionality for Jupiter's moons
Vittorio Serra - Added functionality for Jupiter's moons
Michael Lutz - Added functionality for Jupiter's moons
Ben Dilday <https://github.com/bdilday>__ - Added __hash__()
method to class Epoch
Zivoslav <https://github.com/zivoslav>__ - Bug report of winter
solstice
Devid <https://github.com/sevdog>, Hugo van Kemenade <https://github.com/hugovk> - Test suggestions

What's new

0.5.12
- Fixed a bug in the computation of the winter solstice. Added new
  tests and information about proper use of the library.
0.5.11
- Added parameter local to the Epoch class constructor and
  the methods get_date() and get_full_date().
0.5.10
- Added methods moon_librations() and
  moon_position_angle_axis().
0.5.9
- Added method moon_maximum_declination().
0.5.8
- Fixed several bugs in Epoch class, and added method doy().
0.5.7
- Added method moon_passage_nodes().
0.5.6
- Added method moon_perigee_apogee().
0.5.5
- Added method moon_phase().
0.5.4
- Added methods illuminated_fraction_disk() and
  position_bright_limb() to Moon class.
0.5.3
- Fixed error in the return type of method
  Sun.equation_of_time().
0.5.2
- Added methods to compute the Moon's longitude of ascending node
  and perigee.
0.5.1
- Changes in the organization of the documentation.
0.5.0
- Added Moon class and position() methods.
0.4.3
- Added method ring_parameters() to Saturn class.
0.4.2
- Added method __hash__() to Epoch. Now Epoch objects can be
  used as keys in a dictionary.
0.4.1
- Added funtionality to compute the positions of Jupiter's Galilean
  moons.
0.4.0
- Added methods to compute Saturn's ring inclination and longitude
  of ascending node.
0.3.13
- Additional encoding changes.
0.3.12
- Deleted encoding keyword from setup.py, which was giving
  problems.
0.3.11
- Added encoding specification to setup.py.
0.3.10
- Fixed characters with the wrong encoding.
0.3.9
- Relaxed requirements, added contributor molsen234, and fixed
  format problems showed by flake8.
0.3.8
- Fixed undefined variable in Epoch.tt2ut.
0.3.7
- Fix bug when using fractional seconds, minutes, hours or days,
  plus documentation improvements.
0.3.6
- Add method to compute rising and setting times of the Sun.
0.3.5
- Add method magnitude() to planet classes.
0.3.4
- Add method to compute the parallax correction to Earth class.
0.3.3
- Add methods to compute the passage through the nodes.
0.3.2
- Add methods to compute the perihelion and aphelion of all planets.
0.3.1
- Fix errors in the elongation computation, add tests and examples
  of use of methods geocentric_position(), and tests and
  examples for Pluto class.
0.3.0
- Added Pluto class.

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