Astronomy Calculators
Explore the universe with numbers. Our astronomy calculators help stargazers, students, and space enthusiasts work with the scales and optics of the cosmos. Calculate telescope magnification to choose the right eyepiece, find out how much you would weigh on Mars or Jupiter, convert between light years and other distance units, or look up sunrise and sunset times for any location. All tools are free, instant, and based on established astronomical formulas.
Telescope Magnification Calculator
Calculate magnification, exit pupil, and max useful power for your telescope.
Planet Weight Calculator
Find your weight on any planet in the solar system.
Light Year Calculator
Convert between light years, kilometers, miles, AU, and parsecs.
Sunrise & Sunset Calculator
Find sunrise and sunset times for any location and date.
Frequently Asked Questions
How do I calculate telescope magnification?
Telescope magnification equals the focal length of the telescope divided by the focal length of the eyepiece. For example, a 1200mm telescope with a 25mm eyepiece gives 48x magnification. Our calculator also shows the maximum useful magnification (roughly 2x the aperture in mm) and the exit pupil size for your combination.
How much would I weigh on other planets?
Your weight on another planet depends on that planet's surface gravity relative to Earth. For example, Mars has about 38% of Earth's gravity, so a 70 kg person would weigh about 26.6 kg there. Jupiter's gravity is 2.53 times Earth's, making you feel much heavier. Our planet weight calculator covers all 8 planets plus the Moon and Pluto.
What is a light year and how far is it?
A light year is the distance light travels in one year in a vacuum — approximately 9.461 trillion kilometers or 5.879 trillion miles. It is a unit of distance, not time. Our light year calculator converts between light years, kilometers, miles, astronomical units, and parsecs, helping you grasp the vast scales of the universe.
How are sunrise and sunset times calculated?
Sunrise and sunset times depend on your geographic latitude, longitude, and the date. The calculations use solar declination and the equation of time to determine when the sun crosses the horizon. Our calculator estimates these times for any location and date, accounting for atmospheric refraction that makes the sun visible slightly before it geometrically rises.