Astronomy Calculators
Last updated: September 2026
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.
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.
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.
Apparent Magnitude Calculator
Convert a star's absolute magnitude and distance in parsecs into its apparent magnitude — how bright it looks from Earth.
Stellar Distance Calculator
Convert a star's measured parallax angle into its distance in parsecs, light-years, or astronomical units.
Planetary Angular Distance Calculator
Compute the angular separation in degrees between any two celestial objects using their right ascension and declination coordinates.
Stellar Luminosity Calculator
Compute a star's luminosity in solar units (L☉) from its radius and surface temperature via the Stefan-Boltzmann law.
Planetary Mass Calculator
Determine the mass of a star or planet in solar masses from a satellite's orbital period and semi-major axis.
Habitable Zone Calculator
Estimate the inner edge of a star's habitable zone in AU based on its luminosity 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.
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.
Escape Velocity Calculator
Calculates the escape velocity from a planet, moon, or star — the minimum speed an object needs to break free of its gravity without further propulsion.
Exoplanet Habitability Calculator
Estimate an exoplanet's effective surface temperature and habitability based on its host star and orbital parameters.
Light Travel Time Calculator
Find how long light takes to travel any astronomical distance.
Angular Size Calculator
Calculate how large a celestial object appears in the sky given its physical diameter and distance.
Planetary Temperature Calculator
Estimate a planet's equilibrium temperature based on its host star's temperature, radius, and the planet's orbital distance.
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 and Magnitude Calculator
Determine a star's distance in parsecs from its apparent magnitude, absolute magnitude, and interstellar extinction.
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.
Magnitude Difference Calculator
Convert the difference between two stellar magnitudes into a brightness ratio.
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.
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.
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.
Astrophotography Exposure Calculator
Calculate the recommended sub-frame exposure time for deep-sky astrophotography based on your telescope, camera, and sky conditions.
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.
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.
Asteroid Impact Energy Calculator
Calculate the kinetic energy released when an asteroid strikes Earth, expressed in megatons of TNT.
Planet Visibility Calculator
Find the best times to observe Jupiter, Saturn, Mars, or Venus from your location.
Telescope Magnification Calculator
Calculate the magnification, resolution, and light-gathering power of any telescope from its objective focal length, eyepiece, and aperture.