20 FREE TOOLS · ✦
Astronomy & space calculators
Explore ideal orbits, observing equipment and astronomical scales.
Orbits & escape
Explore ideal two-body orbital relationships.
Explore topic ↗5 calculatorsTelescopes & apparent size
Relate focal length, aperture, magnification and angular size.
Explore topic ↗8 calculatorsAstronomical distance
Explore light time, parallax and distance-related magnitude.
Explore topic ↗All astronomy & space calculators
Kepler Orbital Period Calculator
Estimate a small body’s orbital period around a one-solar-mass star.
Circular Orbit Speed Calculator
Find ideal circular orbital speed around a body using its gravitational parameter.
Escape Velocity Calculator
Find ideal escape speed from a spherical body at a chosen centre distance.
Telescope Magnification Calculator
Find telescope magnification from telescope and eyepiece focal lengths.
Telescope Exit Pupil Calculator
Calculate the diameter of light leaving a telescope eyepiece.
Telescope Focal Ratio Calculator
Calculate optical focal ratio from focal length and aperture.
Angular Size Calculator
Find apparent angular diameter from physical size and distance.
Light Travel Time Calculator
Find time for light to travel a vacuum distance expressed in kilometres.
Parallax Distance Calculator
Estimate stellar distance from annual parallax angle in arcseconds.
Distance Modulus Calculator
Find distance modulus from a distance expressed in parsecs.
Magnitude Flux Ratio Calculator
Compare received flux from a difference in astronomical magnitudes.
Magnitude Difference From Flux Calculator
Convert an astronomical flux ratio into a magnitude difference.
Distance From Modulus Calculator
Recover astronomical distance from an entered distance modulus.
Redshift From Wavelength Calculator
Compare an observed spectral wavelength with its rest wavelength.
Observed Wavelength From Redshift Calculator
Find observed wavelength for a stated rest wavelength and redshift.
Orbital Period From Mu Calculator
Find orbital period from central gravitational parameter and circular-orbit radius.
Surface Gravity From Mu Calculator
Estimate gravity at a spherical body’s surface from its gravitational parameter.
Elliptical Orbit Eccentricity Calculator
Find orbital eccentricity from extreme orbital distances.
Orbit Semi Major Axis Calculator
Find an ellipse’s semi-major axis from periapsis and apoapsis distances.
Telescope True Field Calculator
Estimate sky field of view from apparent eyepiece field and telescope magnification.
Make your inputs count
Use the stated astronomical units and model assumptions. Orbital radius starts at the central body’s centre. These simple models omit many observational uncertainties and real-world perturbations.