40+ free tools for stargazers, students, and space enthusiasts
Find current moon phase and illumination for any date
See where planets are in the sky right now from your location
Generate a star chart for your location and time
Find sunrise, sunset, and twilight times for any location
Check sky darkness and best stargazing spots near you
Evaluate atmospheric stability for astronomical observing
Calculate dark adaptation time and red light recommendations
Find when celestial objects cross your local meridian
Determine magnification and field of view for your telescope
Calculate effective focal length with Barlows and reducers
Determine exit pupil for optimal image brightness
Calculate actual field of view for eyepiece and telescope combos
Calculate stellar distances using parallax and luminosity methods
Compare star brightness using absolute and apparent magnitude
Calculate orbital periods using Kepler's third law
Calculate escape velocity from any celestial body
Find upcoming solar eclipses and visibility from your location
Track upcoming lunar eclipses and their types
Estimate planetary mass from orbital parameters
Find peak dates and expected rates for meteor showers
Calculate delta-v budgets for orbital maneuvers
Estimate travel time to planets and moons at various speeds
Calculate propellant requirements for rocket missions
Plan gravity assist trajectories for interplanetary travel
Calculate orbital period and velocity at any altitude
Determine safe reentry corridor for spacecraft
Calculate optimal exposure time for deep sky objects
Determine acceptable tracking error for focal length
Calculate field curvature for your optical system
Determine plate scale and resolution for your setup
Estimate how long a star will burn based on its mass
Calculate distance using standard candle Type Ia supernovae
Convert redshift to distance and recession velocity
Plot stars on the Hertzsprung-Russell diagram
Compare mass, radius, gravity, and other properties of planets
Calculate surface gravity on any planet or moon
Compare day lengths across all planets in the solar system
Calculate moon orbital periods and distances from parent planet
Estimate kinetic energy of an asteroid impact
Calculate orbital parameters for comets