"Astronomical computations via Astropy. Use when: user asks about celestial coordinates, FITS files, or cosmological calculations. NOT for: telescope control or real-time observation planning."
Astronomical computations using Astropy.
from astropy.coordinates import SkyCoord, EarthLocation, AltAz
from astropy.time import Time
import astropy.units as u
coord = SkyCoord(ra=10.684*u.deg, dec=41.269*u.deg, frame='icrs') # M31
coord_str = SkyCoord('00h42m44.3s', '+41d16m09s', frame='icrs')
# ICRS to Galactic
galactic = coord.galactic
print(f"l={galactic.l:.4f}, b={galactic.b:.4f}")
# Angular separation
c1 = SkyCoord(ra=10.684*u.deg, dec=41.269*u.deg)
c2 = SkyCoord(ra=11.0*u.deg, dec=41.5*u.deg)
sep = c1.separation(c2)
# AltAz (horizontal) coordinates
location = EarthLocation(lat=34.05*u.deg, lon=-118.25*u.deg, height=100*u.m)
time = Time('2026-03-15 03:00:00', scale='utc')
altaz = coord.transform_to(AltAz(obstime=time, location=location))
print(f"Alt={altaz.alt:.2f}, Az={altaz.az:.2f}")
import astropy.units as u
d = 10 * u.pc
print(d.to(u.lyr)) # parsecs to light-years
wav = 21 * u.cm
freq = wav.to(u.GHz, equivalencies=u.spectral())
wavelength = (13.6 * u.eV).to(u.nm, equivalencies=u.spectral())
from astropy.io import fits
with fits.open('image.fits') as hdul:
hdul.info()
header = hdul[0].header
data = hdul[0].data
hdu = fits.PrimaryHDU(data_array)
hdu.header['OBJECT'] = 'M31'
hdu.writeto('output.fits', overwrite=True)
from astropy.cosmology import Planck18 as cosmo
z = 1.0
d_L = cosmo.luminosity_distance(z) # luminosity distance
d_A = cosmo.angular_diameter_distance(z) # angular diameter distance
age = cosmo.age(z) # age of universe at z
lookback = cosmo.lookback_time(z) # lookback time
H_z = cosmo.H(z) # Hubble parameter at z
from astropy.time import Time
import astropy.units as u
t = Time('2026-03-15 12:00:00', scale='utc')
print(t.jd, t.mjd, t.unix) # JD, MJD, Unix
print(t.tai, t.tdb) # TAI, TDB scales
now = Time.now()
python3 -c "
from astropy.coordinates import SkyCoord; import astropy.units as u
c = SkyCoord(ra=83.633*u.deg, dec=22.014*u.deg)
print(f'Galactic: l={c.galactic.l:.3f}, b={c.galactic.b:.3f}')
"
astropy.units.utc, tai, tdb).Planck18 as default cosmology unless otherwise specified.SkyCoord for all coordinate work rather than manual trig.