Astronomy & Navigation Calculators

Sun and moon, celestial, great-circle and navigation tools.

9 tools · 100% Free · Works Offline

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Light Travel Time CalculatorCalculate how long light takes to travel a given distance, from light-minutes to light-years,…

Focal Ratio CalculatorCalculate a telescope or camera lens focal ratio (f-number) from focal length and aperture…

Weight on Other Planets CalculatorFind out what you'd weigh on the Moon, Mars or other planets based on your weight on Earth and…

Escape Velocity CalculatorCalculate escape velocity for Earth, other planets or any custom mass and radius with this free…

All Astronomy & Navigation Calculators (9)

Guide to Astronomy Calculators

These tools cover two overlapping jobs: planning what you can actually see through a telescope, and reasoning about the physics and scale of the solar system and beyond. Amateur astronomers, students and curious hobbyists use them most, but the right choice is rarely obvious because "magnification" alone tells you little — a scope's aperture, focal ratio and the target's angular size together decide whether an object is visible or just a smear.

Setting up a telescope for a session

Start with focal ratio to gauge your scope's speed and field, use magnification for a specific eyepiece pairing, and check max magnification before you push a scope past what its aperture can resolve.

Focal Ratio Calculator Telescope Magnification Calculator Telescope Max Magnification Calculator

Will the target actually fit and resolve

Use angular size to work out how big a planet, moon or deep-sky object appears in the sky, then compare against your eyepiece field and the magnification the optics can support.

Angular Size Calculator Telescope Magnification Calculator Telescope Max Magnification Calculator

Gravity and escape across the solar system

Use the weight tools to compare what you'd weigh on other worlds, and escape velocity when you want the speed needed to leave a body's gravity — handy for physics homework and intuition-building.

Weight on Other Planets Calculator Planet Weight Calculator Escape Velocity Calculator

Cosmic distance and scale

Convert between light-years and everyday distance units for context, and use light travel time when you want to know how long light (or a signal) takes to cross a given gap.

Light-Year Converter Light Travel Time Calculator

Important calculation notice

These calculators are intended for education, estimation and preliminary checks. Verify all inputs, units, assumptions, material properties and applicable standards. Safety-critical or final engineering designs should be checked by a suitably qualified professional.

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Astronomy & Navigation Calculators

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All Astronomy & Navigation Calculators (9)

Optics & Observing4 calculators

Solar System & Gravity3 calculators

Distance & Scale2 calculators

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