Free Tools

Interactive calculators built for backyard stargazing and amateur astronomy for beginners. No sign-up, no downloads — enter your numbers and get an answer you can act on.

Telescope Magnification Calculator

Get magnification, exit pupil, true field of view, and f-ratio for any scope and eyepiece combination.

Moon Phase Calculator

Check the Moon's phase and illumination for any date to plan whether a night favors deep-sky targets or the Moon and planets.