Astrodemia is a free, Duolingo-style astronomy learning app that teaches you to recognize the night sky through daily practice. Our Bortle-adaptive curriculum starts with the stars visible from your city and progressively builds to the full dark-sky experience.
What you learn: 88 IAU constellations, 28 bright named stars (Sirius, Vega, Betelgeuse…), and 11 asterisms and sky skills — Orion's Belt, the Big Dipper, the Pleiades, star-hopping, magnitude reading.
How it works: 15 interactive quiz types (multiple choice, tap-on-sky, lasso, free-text, connect-the-stars, naked-eye timer) powered by the FSRS spaced repetition algorithm. Sessions take 3–5 minutes a day.
Available in English, Español, 中文, 日本語, 한국어, Français, Deutsch, and Português. Offline-first — all progress stored in your browser. Free, no account required.
Start with the constellations your own sky can actually show. Tell Astrodemia which city you observe from and it reads that city's light pollution off the World Atlas of Artificial Night Sky Brightness, then moves the patterns bright enough to survive the skyglow — Orion, the Big Dipper, Cassiopeia — to the front of the queue. The practice sky is dimmed to match, so what you drill is what you will find when you look up. Constellations that genuinely need a darker site are marked rather than hidden, so you know what is waiting on your next trip out of town.
A nine-step scale for how dark a night sky is. Class 1 is a pristine site where the Milky Way casts shadows; class 9 is an inner-city sky with a few dozen stars in it. Each step up costs you roughly half a magnitude of faint stars, which is why the same constellation can be obvious from a village and invisible from a suburb. Astrodemia uses your class to decide which stars are drawn in the practice sky and which lessons come first. Set it by hand, or pick your city and let the light-pollution atlas set it for you.
One session is enough for your first constellation — that is why Astrodemia opens with questions instead of a tutorial. The full catalogue is 88 constellations, 28 named stars and 11 asterisms and sky skills, and that is a project of months, partly because the sky sets the pace: a winter constellation can only be confirmed in winter. A session is twenty questions and takes a few minutes, and the spaced-repetition schedule decides when each thing comes back, so the number that matters is days practised, not hours spent.
No. Everything Astrodemia teaches is naked-eye: the star catalogue stops at magnitude 6.5, roughly the limit of a dark-adapted eye, and the questions ask you to recognise patterns rather than to hunt faint objects. Binoculars are a pleasure on the Pleiades or the Beehive but are never required, and practising needs no equipment at all — the app runs in a browser, indoors, at any hour of the day.
It is free, carries no ads, and has no sign-up screen because there is no server to sign in to. Your streak, your XP and every spaced-repetition card live in your own browser's storage. You can export the whole profile as a JSON file to back it up or move it to another device, and import it on the other side. Nothing about your progress leaves your device unless you export it yourself.
Yes to both. It is a website, so there is nothing to install, though you can add it to a phone's home screen and it will open like an app. After the first visit a service worker keeps the app, the star catalogue and every language on the device, so a session runs with the network switched off. That is deliberate: the darkest skies are usually the places with the worst signal.
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