Astronomy & cosmology, at your fingertips.
Quick, transparent calculators for common astronomical conversions. Cosmological quantities share one parameter set; results are estimates under the model shown.
Set the background cosmology used by all redshift-based distance and time tools.
Assumes spatially flat ΛCDM: ΩΛ = 1 − Ωm − Ωr. Radiation defaults to zero for low-redshift work. A negative ΩΛ is permitted mathematically, but may not describe the cosmology you intend.
Comoving, angular-diameter and luminosity distances, plus lookback time and cosmic age.
Convert an angular diameter to a transverse physical size using Dₐ(z).
Bolometric or band-integrated flux and luminosity, without a K-correction.
Apparent ↔ absolute magnitude from luminosity distance.
Observed/rest wavelength conversion for spectral features.
Special-relativistic Doppler conversion for a radial velocity interpretation.
This is a Doppler-equivalent velocity, not a general cosmological recession velocity. For nearby objects, peculiar velocity corrections and the adopted frame (heliocentric, barycentric, CMB) matter.
Convert AB magnitude and fν in Jy, mJy or μJy.
Estimate Aᵦ = Rᵦ × E(B−V) using a selectable coefficient.
Coefficients are approximate and depend on the adopted extinction law, bandpass and source SED. Apply to Galactic foreground only; internal attenuation is a separate correction.
Parse sexagesimal coordinates with sign and range checks.
Great-circle separation between two sky positions.
Calendar date and time in UTC → JD and MJD.
This uses the browser's date input fields as UTC calendar components; leap-second representation is not supported.
Transform ICRS/J2000 equatorial coordinates to Galactic longitude and latitude.
Kasten–Young approximation from target altitude.
The approximation is not intended for targets at or below the horizon; near-horizon atmospheric conditions are especially uncertain.
Useful constants and common distance conversions.