astronomy Calculators
Last updated: May 2026
Stellar Luminosity Calculator
Compute a star's luminosity in solar units (L☉) from its radius and surface temperature via the Stefan-Boltzmann law.
Distance Modulus Calculator
Compute distance to a celestial object in parsecs from its apparent and absolute magnitudes using the distance modulus formula d = 10^((m − M + 5)/5).
Orbital Velocity Calculator
Compute the orbital velocity around a central body using v = √(GM/r) × √(1+e), an approximation that scales the circular-orbit speed by the eccentricity.
Schwarzschild Radius Calculator
Compute the Schwarzschild radius — the event horizon size of a non-rotating black hole — from its mass via r_s = 2GM/c².
Redshift Velocity Calculator
Compute the recession velocity of a nearby galaxy from its redshift z using v = c·z, where c is the speed of light.
Planetary Mass Calculator
Determine the mass of a star or planet in solar masses from a satellite's orbital period and semi-major axis.
Escape Velocity Calculator
Find the minimum speed an object must reach to escape a celestial body's gravity without further propulsion.
Stellar Parallax Calculator
Convert a star's measured parallax angle into its distance from Earth in parsecs.
Tidal Force Calculator
Calculate the gravitational force between two celestial bodies separated by a given distance.
Habitable Zone Calculator
Estimate the inner edge of a star's habitable zone in AU based on its luminosity relative to the Sun.
Light Travel Time Calculator
Find how long light takes to travel any astronomical distance.
Magnitude Difference Calculator
Convert the difference between two stellar magnitudes into a brightness ratio.
Angular Size Calculator
Calculate how large a celestial object appears in the sky given its physical diameter and distance.
Roche Limit Calculator
Find the critical orbital distance inside which a satellite is torn apart by tidal forces.
Synodic Period Calculator
Calculate how long it takes two orbiting bodies to return to the same relative position in the sky.
Stellar Lifetime Calculator
Estimate how long a star spends on the main sequence based on its mass relative to the Sun.
Comet Perihelion Velocity Calculator
Calculate a comet's maximum speed at perihelion — its closest point to the Sun — using the vis-viva equation.
Galactic Year Calculator
Calculate how long it takes a star or object to complete one full orbit around the galactic center, given its orbital radius and velocity.
Apparent Magnitude Calculator
Convert a star's absolute magnitude and distance in parsecs into its apparent magnitude — how bright it looks from Earth.
Planetary Temperature Calculator
Estimate a planet's equilibrium temperature based on its host star's temperature, radius, and the planet's orbital distance.
Telescope Magnification Calculator
Compute the effective magnification of your telescope with any eyepiece and Barlow lens combination.
Planetary Transit Calculator
Estimate when inner planets Mercury and Venus will cross the disk of the Sun as seen from a specific location on Earth.
Light Pollution Sky Quality Calculator
Estimate the faintest star visible through your telescope by combining sky brightness, aperture, altitude, observer age, and moon phase.
Stellar Distance Calculator
Convert a star's measured parallax angle into its distance in parsecs and light-years using the standard parallax formula.
Exoplanet Habitability Calculator
Estimate an exoplanet's effective surface temperature and habitability based on its host star and orbital parameters.
Astrophotography Exposure Calculator
Calculate the recommended sub-frame exposure time for deep-sky astrophotography based on your telescope, camera, and sky conditions.
Meteor Shower Activity Calculator
Estimate how many meteors per hour you will actually see during a meteor shower, accounting for radiant altitude, sky darkness, and moonlight.
Stellar Distance Calculator
Convert a star's measured parallax angle into its distance in parsecs, light-years, or astronomical units.
Planet Visibility Calculator
Find the best times to observe Jupiter, Saturn, Mars, or Venus from your location.
Lunar Phase Calculator
Calculate the Moon's current phase and illumination percentage for any calendar date.
Solar Eclipse Duration Calculator
Estimate how long totality or partial coverage will last at your location during a solar eclipse.
Asteroid Impact Energy Calculator
Calculate the kinetic energy released when an asteroid strikes Earth, expressed in megatons of TNT.
Exoplanet Habitable Zone Calculator
Estimate the inner and outer boundaries of a star's habitable zone based on its luminosity, spectral type, and a planet's mass.
Planetary Angular Distance Calculator
Compute the angular separation in degrees between any two celestial objects using their right ascension and declination coordinates.
Stellar Distance and Magnitude Calculator
Determine a star's distance in parsecs from its apparent magnitude, absolute magnitude, and interstellar extinction.