Good questions.
Clearer skies.

Yes. Epicycle is completely free. There are no advertisements, paid upgrades, in-app purchases, or subscriptions. All 88 constellations, astronomical lessons, unified Sky tab, and the 70+ question quiz bank are unlocked for everyone. The optional charity link on our website supports No Stomach For Cancer and is completely separate from the app.

Epicycle is officially live on the Apple App Store for iPhone and iPad (requires iOS 17.0+). You can download it directly using the App Store button on this site. An Android version (Android 10+) is currently in active development, and upcoming release updates will be posted here.

• iOS / iPadOS: Requires iOS 17.0 or later on compatible iPhone and iPad devices. • Android: Requires Android 10.0 (API Level 29) or later with camera and motion sensor support. For the optional Live Sky camera overlay, a physical device equipped with a rear camera, accelerometer, and magnetic compass is required.

No account or login is required. The star catalog, constellation illustrations, educational lessons, and sky map are bundled inside the app and function 100% offline. You can use Epicycle anywhere—including dark-sky parks, remote campsites, and classrooms without internet.

All educational lessons, the complete 88-constellation catalog, the 70+ question space quiz bank, and the interactive offline Sky tab work without granting camera or location permissions. On the Sky Map, you can toggle between preset world observatories (New York, London, Tokyo, Sydney, Cape Town, Quito) and customize observing dates/times manually.

Epicycle combines the star map and live AR view into a single Sky tab. You can toggle between Map and Camera modes with one tap. In Camera mode, point your device at the sky to see simulated constellation lines and planets overlaid on the real world. Use the 'Align to object in circle' feature or manual heading controls (+/- 0.1°) to lock in alignment against the Moon or a known bright star.

Compass accuracy is subject to local magnetic fields and interference: • Quick In-App Alignment: In Camera mode, expand 'Adjust alignment', center the Moon, a planet, or a bright star in the alignment circle, tap 'Align to object in circle', and hold steady for a moment. You can also nudge heading manually with +/- 0.1° buttons. • On iOS: Verify that Settings > Privacy & Security > Location Services > System Services > Compass Calibration is turned ON. • On Android: Perform a gentle figure-8 motion in the air with your device for 5–10 seconds to recalibrate the magnetometer. • Always step away from metal railings, vehicles, electrical conduits, and magnetic phone cases.

Epicycle includes a comprehensive 70+ question quiz bank divided into two tiers: • Explorer: Designed for young stargazers (ages 6–9), focusing on intuitive celestial concepts and picture questions. • Astronomer: Designed for older kids and curious adults (ages 10+), exploring stellar lifecycles, planetary physics, and astronomical geometry. Every question includes clear explanations, live calculations (such as today's Moon phase), and 'See it in the app' deep links into object cards.

Epicycle calculates simulated celestial positions based on astronomical orbital mechanics. Real-world visibility is affected by daylight, weather clouds, light pollution, local horizon obstructions (buildings/trees), and the object’s current visual magnitude. Make sure your viewing time and location are correctly set.

Epicycle was built with curious families and students in mind. There is zero data collection, no ads, no social posting, and no tracking. When stargazing at night outdoors, young children should always be supervised by an adult.