Astronomy Tools

Free astronomy and space calculators that run entirely in your browser — your weight and age on other planets, telescope magnification and resolving power, pixel scale, light-year distance, redshift, orbital period, angular size, stellar parallax, apparent/absolute magnitude, Schwarzschild radius and delta-v. No sign-up, nothing uploaded.

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Weight on Other Planets Calculator

See what you'd weigh on the Moon, Mars, Jupiter, the Sun and every planet — just enter your Earth weight to read all ten worlds at once.

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Age on Other Planets Calculator

Convert your Earth age into years on Mercury, Venus, Mars, Jupiter, Saturn, Uranus and Neptune — enter your age or your birth date.

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Telescope Magnification & Exit Pupil Calculator

Find magnification, exit pupil, true field of view, focal ratio and the maximum useful power for any telescope and eyepiece pairing.

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Light-Year & Light Travel Time Calculator

Convert a distance between light-years, parsecs, astronomical units, kilometres and miles, and get the one-way light travel time.

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Telescope Resolving Power Calculator (Dawes / Rayleigh)

Find a telescope's angular resolution (Dawes and Rayleigh limits), limiting magnitude and light-gathering power from its aperture alone.

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CCD Pixel Scale Calculator (arcsec/pixel)

Calculate image scale in arcseconds per pixel and the field of view for an astro camera on a telescope, from pixel size and focal length.

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Redshift & Recession Velocity Calculator

Turn a spectral redshift z (or observed and rest wavelengths) into recession velocity and Hubble distance, with an adjustable Hubble constant.

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Schwarzschild Radius (Black Hole) Calculator

Compute a black hole's Schwarzschild radius (event horizon) from any mass in kilograms, Earth masses, or solar masses, plus its Hawking temperature.

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Magnitude & Distance Modulus Calculator

Solve apparent magnitude, absolute magnitude, or distance from the distance modulus m−M = 5·log₁₀(d)−5, or compare two stars' brightness ratio.

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Orbital Period Calculator (Kepler's Third Law)

Find an orbital period or semi-major axis from Kepler's third law T = 2π√(a³/GM), for any central mass in kilograms, Earth masses, or solar masses.

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Angular Size Calculator

Solve any of physical size, distance, or apparent angle from θ = 2·arctan(size/2·distance); results in degrees, arcminutes, and arcseconds.

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Stellar Parallax Distance Calculator

Convert a star's parallax angle to distance in parsecs, light-years, and AU with d = 1/p, or find the parallax from a known distance.

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Rocket Delta-V Calculator (Tsiolkovsky)

Compute rocket delta-v from the Tsiolkovsky equation Δv = Isp·g₀·ln(m₀/m_f), or solve wet mass, dry mass, mass ratio, and propellant fraction.

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