---
id: skyfield-data
version: "7.0.0"
license: MIT
license_treatment: permissive
maintenance: aging
---

# skyfield-data — Data package for Skyfield

License: permissive · Maintenance: aging · Downloads: 98.9K/mo

## What it is and what it does

skyfield-data is a data distribution package that bundles the ephemeris and Earth rotation files required for astronomical calculations. Instead of having dependent libraries download these large files at runtime (which can cause delays, timeouts, or network failures), this package installs them locally via pip, allowing offline computation and eliminating dependency on NASA JPL or IERS availability.

The package includes de421.bsp (planetary ephemeris) and finals2000A.all (Earth orientation data), with built-in expiration tracking. When you instantiate a Loader pointing to the data path provided by this package, computations use the local files without triggering downloads. The package emits warnings when files approach or pass their expiration dates, signaling when an upgrade is needed to maintain accuracy.

Use it for:

- Offline astronomical computation in environments without reliable internet access or behind restrictive network proxies.
- Web applications requiring predictable startup time and avoiding runtime downloads that could timeout client requests.
- Containerized deployments where reproducible, pre-cached data files reduce image size and startup latency.
- Long-running services that need to compute moon phases, planet positions, or timescale data without external dependencies.
- Development and testing workflows where consistent, versioned data ensures reproducible astronomical calculations.

## Worth the install?

AI-flagged interpretation of the facts above — verify before relying.

Provides pre-packaged astronomical data files (ephemerides and Earth rotation data) for offline use, eliminating runtime downloads and network dependencies.

Yes, if you need offline astronomical data files. Install alongside dependent libraries and point loaders to its data path. Be aware that data files expire (de421.bsp in 2053, finals2000A.all in 2026); you must upgrade the package before expiration to maintain accuracy. The 353-day gap since the last release suggests maintenance is not rapid, so monitor expiration dates and plan upgrades accordingly.

## Install

pip install skyfield-data
uv add skyfield-data
poetry add skyfield-data

## Installing skyfield-data

Before you install: Low friction installation as a pure data wheel with no runtime dependencies. Last release was 353 days ago; the package is in aging maintenance status. Repository is not archived and receives commits.

License in practice: MIT license permits unrestricted use, modification, and distribution. Data files themselves (de421.bsp from JPL, finals2000A.all from IERS) are provided under their respective institutional terms; the Python package code is MIT-licensed.

Quickstart:

pip install skyfield-data

from skyfield_data import get_skyfield_data_path
from skyfield.api import Loader
load = Loader(get_skyfield_data_path())
planets = load('de421.bsp')

Data files have expiration dates (de421.bsp expires 2053-10-08, finals2000A.all expires 2026-10-18); package must be upgraded before expiration to avoid stale data.

Verify before relying:

- Whether all data files in version 7.0.0 remain within their expiration windows as of August 2026.
- Current compatibility status with Python 2.6 given the noted defunct CI for that version.
- Whether the package is actively maintained or in maintenance-only mode given the 353-day release gap.
- How frequently this package is updated relative to data file expiration schedules.

## Package facts

- License: MIT (permissive)
- Python support: supports_current
- Install friction: low
- Maintenance: aging
- Downloads: 98.9K/month (top 15,000 on PyPI)
- Known vulnerabilities: none known

## Tags

astronomical data files offline, ephemeris data package, pre-downloaded astronomy assets, JPL ephemeris offline, earth rotation data package, de421 finals2000a data, astronomy computation data, astronomy, offline-data, ephemeris

[View on SkillFed](https://skillfed.io/packages/skyfield-data) · [View on PyPI](https://pypi.org/project/skyfield-data/)