8 astronomy and telescope calculators.
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Magnification, exit pupil and useful range from scope, eyepiece and Barlow.
Solve focal length, aperture or f/number from the other two.
Sky the eyepiece shows: apparent field / magnification, with Moon widths.
Exit pupil from aperture / magnification or eyepiece / focal ratio.
Telescope resolving power (Dawes 116/D, Rayleigh 138/D) from aperture.
Faintest stars a telescope shows, plus light grasp vs the naked eye.
Convert light-years, parsecs, AU, km and miles, with light travel time.
Arcsec/pixel, sensor field of view and sampling verdict for astrophotography.
A set of astronomy calculators for visual observing and astrophotography: telescope magnification with Barlow and exit pupil, focal ratio, the true field of view of an eyepiece, Dawes and Rayleigh resolution limits, limiting magnitude, a light-year / parsec / AU distance converter, and the pixel scale and sampling of a camera-telescope combination. Standard optics maths, all in your browser.
They use the standard formulas: magnification = focal length ÷ eyepiece, exit pupil = aperture ÷ magnification, Dawes 116/D, the classic 7.7 + 5·log10(D cm) limiting-magnitude estimate, IAU-exact distance constants and pixel scale = 206.265 × µm ÷ mm. Real-world results shift with seeing, sky darkness and your eyes; the notes on each tool say how.
No. Every calculator runs entirely in your browser with no download, sign-up, or data leaving your device.
Telescope magnification, focal ratio, true field of view, exit pupil, Dawes limit, limiting magnitude, astronomical distances and pixel scale.