Because two components of the position vector are used to finish
building the velocity vector, it was a mistake to rotate the position
vector using the M matrix until after the velocity vector has also been
built. This increases by almost two magnitudes the agreement between
Earth satellite reported velocities and the actual difference between
their successive positions.
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====================================
Welcome to the Skyfield Repository
====================================
Skyfield is a pure-Python astronomy package
that is compatible with both Python 2 and 3
and makes it easy to generate high precision research-grade
positions for planets and Earth satellites.
.. code-block:: python
from skyfield.api import load
planets = load('de421.bsp')
earth, mars = planets['earth'], planets['mars']
ts = load.timescale(builtin=True)
t = ts.now()
position = earth.at(t).observe(mars)
ra, dec, distance = position.radec()
print(ra)
print(dec)
print(distance)
The result:
::
10h 47m 56.24s
+09deg 03' 23.1"
2.33251 au
Skyfield’s only binary dependency is NumPy.
Once that is available, Skyfield can usually be installed with::
pip install skyfield
Here are the essential project links:
* `Home page and documentation
<http://rhodesmill.org/skyfield>`_.
* `Installing Skyfield
<http://rhodesmill.org/skyfield/installation.html>`_.
* `Contributing to Skyfield
<https://github.com/skyfielders/python-skyfield/blob/master/Contrib.rst>`_.
* `Skyfield package <https://pypi.python.org/pypi/skyfield>`_
on the Python Package Index.
* `Issue tracker
<https://github.com/brandon-rhodes/python-skyfield/issues>`_
on GitHub.
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