Data package for Skyfield
Data files for Skyfield
Skyfield is a Python library for astronomical computations. It depends on various data files to accurately compute moon phases, planet positions, etc.
Several issues are raised by these data files:
- If they're not found in the path of the
Loader, they're downloaded at runtime. Depending on the archive you're requesting, some files might be very large, causing a long delay (directly related to your network bandwidth). In the case of a web server app, you'd cause a timeout on client's end.
- They come mainly from 3 sources: the USNO (US Navy), Paris (Meudon) Observatory, and NASA JPL. If one of them is temporarily unavailable, you couldn't perform any computation.
- In some countries, or behind some filtering proxies, the USNO is considered as a military website, and thus is blocked.
- These files have an expiration date (in a more or less distant future). As a consequence, even if the files are already downloaded in the right path, at each runtime you could possibly have to download one or more files before making any computation using them.
Currently known expiration dates
Goal for this project
- Providing at least the most common of these assets in Python Package.
- Make regular releases to refresh the files before they expire.
- Provide a warning / logging mechanism when the files are about to expire (or when they are outdated) to still allow you to compute things with the loaded assets, but being informed you need to upgrade.
This way, you could install or upgrade this data package via
Once all the files are on your disk space, you can instantiate your
skyfield loader pointing at their path, without having to worry about anything.
Install the packages using:
pip install skyfield skyfield-data
To create a custom Skyfield loader, use the following code:
from skyfield_data import get_skyfield_data_path from skyfield.api import Loader load = Loader(get_skyfield_data_path()) planets = load('de421.bsp') # this command won't download this file ts = load.timescale() # this command won't download the deltat + Leap Second files
If you want to make sure that the data files would never be downloaded, you can also use the
expire option like this:
load = Loader(get_skyfield_data_path(), expire=False)
Whenever a file contained in the catalog has expired, you're going to receive a warning when loading the
>>> from skyfield_data import get_skyfield_data_path >>> from skyfield.api import Loader >>> load = Loader(get_skyfield_data_path()) /home/[redacted]/skyfield_data/expirations.py:25: RuntimeWarning: The file de421.bsp has expired. Please upgrade your version of `skyfield-data` or expect computation errors RuntimeWarning
By default, the loading isn't blocked, but it's strongly recommended to upgrade to a more recent version, to make sure you're not going to make wrong astronomical computations.
We're providing a
Makefile with basic targets to play around with the toolkit. use
make help to get more details.
In order to be able to run the
download.py script, we recommend to run it from a virtualenv where you'd have installed the "dev" dependencies, using:
Note: This project is, and should be compatible with Python 2.6/2.7 and Python 3.5+, to be kept the same Python compatiblity that
de421.bspis provided by the Jet Propulsion Laboratory,
deltat.predsare provided by the United States Naval Observatory,
Leap_Second.datis provided by the International Earth Rotation and Reference Systems Service.
This Python Package code is published under the terms of the MIT license. See the
COPYING file for more details.
Download the file for your platform. If you're not sure which to choose, learn more about installing packages.
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|Filename, size skyfield_data-0.1.0-py2.py3-none-any.whl (16.0 MB)||File type Wheel||Python version py2.py3||Upload date||Hashes View hashes|
|Filename, size skyfield-data-0.1.0.tar.gz (16.0 MB)||File type Source||Python version None||Upload date||Hashes View hashes|
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