Free Online Astronomy Tools
Explore telescope optics, star distances, brightness and orbital relationships with online astronomy calculators.
Choose the right tool
Use telescope calculators for focal lengths and angular scale, magnitude tools for logarithmic brightness relationships, and orbit tools for the specified gravitational model. Check whether a distance is in parsecs, light-years or astronomical units.
Available tools
- Telescope Eyepiece Magnification Calculator
Online telescope eyepiece magnification calculator. Idealized astronomical model with displayed units. Seeing, extinction, instrument losses or cosmological effects apply only when explicitly included.
- Telescope Exit Pupil Calculator
Online telescope exit pupil calculator. Idealized astronomical model with displayed units. Seeing, extinction, instrument losses or cosmological effects apply only when explicitly included.
- Eyepiece True Field Approximation
Online eyepiece true field approximation. Idealized astronomical model with displayed units. Seeing, extinction, instrument losses or cosmological effects apply only when explicitly included.
- Eyepiece Field Stop Angular Field
Online eyepiece field stop angular field. Idealized astronomical model with displayed units. Seeing, extinction, instrument losses or cosmological effects apply only when explicitly included.
- Telescope Airy Disk Angular Radius
Online telescope airy disk angular radius. Idealized astronomical model with displayed units. Seeing, extinction, instrument losses or cosmological effects apply only when explicitly included.
- Dawes Telescope Resolution Estimate
Online dawes telescope resolution estimate. Empirical equal-brightness double-star estimate, not a seeing forecast.
- Astronomy Pixel Plate Scale Calculator
Online astronomy pixel plate scale calculator. Idealized astronomical model with displayed units. Seeing, extinction, instrument losses or cosmological effects apply only when explicitly included.
- Astronomical Sensor Angular Field
Online astronomical sensor angular field. Idealized astronomical model with displayed units. Seeing, extinction, instrument losses or cosmological effects apply only when explicitly included.
- Telescope Focal Ratio Calculator
Online telescope focal ratio calculator. Idealized astronomical model with displayed units. Seeing, extinction, instrument losses or cosmological effects apply only when explicitly included.
- Thin Negative Lens Barlow Factor
Online thin negative lens barlow factor. Idealized astronomical model with displayed units. Seeing, extinction, instrument losses or cosmological effects apply only when explicitly included.
- Focal Plane Airy Disk Diameter
Online focal plane airy disk diameter. Idealized astronomical model with displayed units. Seeing, extinction, instrument losses or cosmological effects apply only when explicitly included.
- Telescope Light Collection Ratio
Online telescope light collection ratio. Idealized astronomical model with displayed units. Seeing, extinction, instrument losses or cosmological effects apply only when explicitly included.
- Aperture Magnitude Gain Estimate
Online aperture magnitude gain estimate. Idealized astronomical model with displayed units. Seeing, extinction, instrument losses or cosmological effects apply only when explicitly included.
- Stellar Distance Modulus Calculator
Online stellar distance modulus calculator. Idealized astronomical model with displayed units. Seeing, extinction, instrument losses or cosmological effects apply only when explicitly included.
- Stellar Parallax Distance Calculator
Online stellar parallax distance calculator. Idealized astronomical model with displayed units. Seeing, extinction, instrument losses or cosmological effects apply only when explicitly included.
- Absolute Magnitude from Apparent Magnitude
Online absolute magnitude from apparent magnitude. Idealized astronomical model with displayed units. Seeing, extinction, instrument losses or cosmological effects apply only when explicitly included.
- Astronomical Magnitude Flux Ratio
Online astronomical magnitude flux ratio. Idealized astronomical model with displayed units. Seeing, extinction, instrument losses or cosmological effects apply only when explicitly included.
- Isotropic Stellar Luminosity from Flux
Online isotropic stellar luminosity from flux. Idealized astronomical model with displayed units. Seeing, extinction, instrument losses or cosmological effects apply only when explicitly included.
- Blackbody Stellar Radius Estimate
Online blackbody stellar radius estimate. Idealized astronomical model with displayed units. Seeing, extinction, instrument losses or cosmological effects apply only when explicitly included.
- Blackbody Wien Peak Wavelength
Online blackbody wien peak wavelength. Idealized astronomical model with displayed units. Seeing, extinction, instrument losses or cosmological effects apply only when explicitly included.
- Schwarzschild Radius Calculator
Online schwarzschild radius calculator. Idealized astronomical model with displayed units. Seeing, extinction, instrument losses or cosmological effects apply only when explicitly included.
- Planet Surface Gravity in Earth Units
Online planet surface gravity in earth units. Idealized astronomical model with displayed units. Seeing, extinction, instrument losses or cosmological effects apply only when explicitly included.
- Elliptical Orbit Vis Viva Speed
Online elliptical orbit vis viva speed. Idealized astronomical model with displayed units. Seeing, extinction, instrument losses or cosmological effects apply only when explicitly included.
- Kepler Elliptical Eccentric Anomaly Solver
Online kepler elliptical eccentric anomaly solver. Idealized astronomical model with displayed units. Seeing, extinction, instrument losses or cosmological effects apply only when explicitly included.
- Elliptical Orbit Periapsis and Apoapsis
Online elliptical orbit periapsis and apoapsis. Idealized astronomical model with displayed units. Seeing, extinction, instrument losses or cosmological effects apply only when explicitly included.
- Planetary Synodic Period Calculator
Online planetary synodic period calculator. Idealized astronomical model with displayed units. Seeing, extinction, instrument losses or cosmological effects apply only when explicitly included.
- Relativistic Radial Redshift Velocity
Online relativistic radial redshift velocity. Special-relativistic radial Doppler interpretation, not cosmological recession velocity.
- Low Redshift Hubble Distance Estimate
Online low redshift hubble distance estimate. Linear low-redshift approximation; not a full cosmological distance calculation.
- Stellar Flux Zone Distance Calculator
Online stellar flux zone distance calculator. User-supplied flux limits; does not establish planetary habitability.
- Opaque Planet Transit Depth Calculator
Online opaque planet transit depth calculator. Uniform stellar disk, central unobscured transit; limb darkening excluded.