Amateur Astronomy
Telescope comparisons, eyepiece sets, star parties, Bortle / limiting magnitude, solar filters, mount payload, collimation, deep sky, comets, and meteor showers.
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Age on Other Planets
Find out how old you would be on every planet in our solar system. Your age depends on each planet's orbital period around the Sun.
Collimation Calculator
Calculate secondary mirror offset and collimation tolerance for Newtonian reflectors.
Comet Brightness Calculator
Predict a comet's apparent magnitude based on absolute magnitude and distances from Earth and Sun.
Deep Sky Finder Calculator
Estimate how many galaxies, nebulae, and star clusters are observable with your telescope from your location.
Eyepiece Collection Calculator
Plan a 3-eyepiece set for your telescope with low, medium, and high power focal lengths.
Light Pollution Calculator
Estimate naked-eye and telescope limiting magnitude and SQM reading based on Bortle class, altitude, and moon phase.
Meteor Shower Calculator
Predict how many meteors you will actually see per hour based on shower ZHR, radiant altitude, and sky conditions.
Mount Payload Calculator
Check if your telescope and accessories are within your mount's payload capacity for visual or imaging use.
Solar Filter Calculator
Size a solar filter for safe sun observation and estimate solar image size and cost by filter type.
Star Party Planner Calculator
Plan a star party by estimating sunset time, moon phase, visible planets, and observable deep-sky objects for your location and date.
Telescope Comparison Calculator
Compare two telescopes by f/ratio, light-gathering power, and angular resolution.