astropy
Core Python library for astronomy — provides tools for astronomical calculations, data formats, and coordinate systems. astropy features: astropy.units for physical unit tracking (u.meter, u.km/u.s), astropy.coordinates for sky coordinate systems (SkyCoord, FK5, ICRS, Galactic), astropy.time for precise astronomical time (Time, TimeDelta), astropy.io.fits for FITS file I/O, astropy.table for heterogeneous tabular data, astropy.wcs for world coordinate system transformations, astropy.cosmology for cosmological calculations, astropy.stats for robust statistics, Quantity objects that carry units through calculations, and coordinate frame conversions. The foundation of scientific Python astronomy.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
Local scientific library. Downloads IERS tables from IERS servers on first use — ensure HTTPS. FITS files can contain arbitrary data — validate file sources. No network calls for core functionality after IERS download.
⚡ Reliability
Best When
Astronomical data processing and analysis — astropy is the standard foundation for Python astronomy, providing units, coordinates, time, FITS I/O, and cosmology in one coherent package.
Avoid When
General scientific computing without astronomical context (use numpy/scipy), real-time telescope control, or when only unit tracking is needed (use pint instead).
Use Cases
- • Agent sky coordinate lookup — from astropy.coordinates import SkyCoord; import astropy.units as u; coord = SkyCoord(ra=83.8221*u.degree, dec=-5.3911*u.degree, frame='icrs'); galactic = coord.galactic; print(galactic.l, galactic.b) — coordinate transform; agent converts between ICRS, FK5, Galactic, AltAz coordinate frames; SkyCoord handles all transforms transparently
- • Agent FITS file reading — from astropy.io import fits; hdul = fits.open('image.fits'); header = hdul[0].header; data = hdul[0].data; hdul.close() — FITS I/O; agent reads astronomical FITS data files with full header metadata; hdul is a list of HDUs; data is numpy array; use with context manager: with fits.open('f.fits') as hdul
- • Agent unit-aware calculation — import astropy.units as u; distance = 100 * u.parsec; velocity = 50 * u.km/u.s; time = (distance / velocity).to(u.Myr) — unit tracking; agent performs astrophysical calculations where units are carried automatically; UnitConversionError raised on incompatible units; prevents dimensional analysis bugs
- • Agent precise time handling — from astropy.time import Time; t = Time('2024-01-15T12:00:00', format='isot', scale='utc'); t_tai = t.tai; jd = t.jd; mjd = t.mjd — astronomical time; agent working with astronomical observations converts between UTC, TAI, TDB, Julian Date, MJD; Time handles leap seconds correctly
- • Agent cosmological calculations — from astropy.cosmology import Planck18; z = 0.5; distance = Planck18.luminosity_distance(z); age = Planck18.age(z) — cosmology; agent computes cosmological distances, ages, volumes for given redshifts; Planck18 uses current best-fit cosmological parameters; other: FlatLambdaCDM for custom cosmology
Not For
- • General data science — astropy is specialized for astronomy; for general scientific computing use scipy/numpy directly
- • Real-time observing control — astropy provides calculations not telescope control; for observatory automation use INDI or AstroPy affiliated packages
- • Non-astronomical applications — unit tracking is available but scipy.units or pint are more general purpose
Interface
Authentication
No auth — local scientific library. Some subpackages download data files on first use (IERS tables).
Pricing
astropy is BSD 3-Clause licensed. Free for all use including commercial.
Agent Metadata
Known Gotchas
- ⚠ IERS table download on first use — astropy downloads International Earth Rotation Service tables on first coordinate transform in a session; this requires internet access; agent code in air-gapped environments: from astropy.utils import iers; iers.conf.auto_download = False; or pre-download: astropy.utils.data.download_file(IERS_A_URL)
- ⚠ Quantity math requires compatible units — 1*u.meter + 1*u.second raises UnitConversionError; agent code must ensure dimensional consistency; to get plain float: quantity.value or float(quantity.to(target_unit).value; mixing Quantity with plain float produces another Quantity; common mistake: len(array) * u.second vs np.arange(n) * u.second
- ⚠ SkyCoord distance required for 3D operations — SkyCoord(ra, dec) is 2D; separation() works; separation_3d() requires distance= parameter; agent code computing 3D separations must include distance: SkyCoord(ra=ra*u.deg, dec=dec*u.deg, distance=d*u.pc); without distance, 3D methods raise AttributeError
- ⚠ FITS indexing is 1-based in headers but 0-based in data arrays — FITS standard uses 1-based column/row numbering in header keywords (NAXIS1, CRPIX1); but hdul[0].data is numpy array with 0-based indexing; agent code must not use header pixel values directly as numpy indices without subtracting 1
- ⚠ astropy.table.Table not pandas DataFrame — Table has similar API but different; table['col'] returns Column not Series; table.to_pandas() converts; from_pandas() imports; agent code cannot use pandas methods directly on Table; sorting: table.sort('col'); filtering: table[table['col'] > 0] — mask indexing like pandas but different underlying type
- ⚠ Time scale matters for precision — Time('2024-01-01', scale='utc') vs scale='tai' differ by ~37 seconds (accumulated leap seconds); agent code doing precise time arithmetic must specify scale; default scale is 'utc'; for highest precision astronomical work use scale='tdb' (Barycentric Dynamical Time); mixing scales requires explicit conversion: t.tdb
Full Evaluation Report
Comprehensive deep-dive: security analysis, reliability audit, agent experience review, cost modeling, competitive positioning, and improvement roadmap for astropy.
AI-powered analysis · PDF + markdown · Delivered within 30 minutes
Package Brief
Quick verdict, integration guide, cost projections, gotchas with workarounds, and alternatives comparison.
Delivered within 10 minutes
Score Monitoring
Get alerted when this package's AF, security, or reliability scores change significantly. Stay ahead of regressions.
Continuous monitoring
Scores are editorial opinions as of 2026-03-06.