Celestial Spheres

Celestial Spheres brings the history, geometry, and observation of astronomy into one interactive experience.

Compare five models of the cosmos:

- Ptolemaic: Earth-centered deferents and epicycles.
- Copernican: a Sun-centered system built from compound circular motion.
- Tychonic: a fixed Earth with the Sun carrying the planetary system.
- Keplerian: historical heliocentric ellipses and historical distance scale.
- Modern Astronomy: modern distances, orbital data, and stellar catalogue data.

Move through each model in a real-time 3D simulator. Select and track celestial bodies, inspect annual and daily paths, study model-specific distances and speeds, compare true-scale separation, and examine Earth's day, night, twilight, seasons, phases, eclipse geometry, and analemma.

The Sky Observatory uses your chosen date, time, and optional location to show the visible sky with horizon coordinates, constellation lines and artwork, searchable stars and planets, object tracking, Moon phases, ecliptic and lunar paths, RA/declination, and wide-angle sky views. Set observer height from 1 metre to 500 km and explore pressure- and temperature-dependent atmospheric refraction.
Pro AR Observatory (Beta) overlays the sky on a live rear-camera preview on supported devices. Compass and lens calibration affect alignment; camera images are not recorded or uploaded. Never look directly at the Sun.

Specialist tools include:

- A 5,000-year solar and lunar Eclipse Atlas with Saros families.
- A model-by-model Retrograde Explorer with event playback and apparent paths.
- A close-approach atlas for comets and asteroids with distance and speed data.
- Selected comet and asteroid orbits integrated into the simulator.
- Clearly labelled approximate orbit demonstrations outside verified data coverage.
- A Mechanisms Lab covering satellites, gyroscopes, Coriolis effects, and weight at different latitudes and altitudes, with illustrated equations.
- Planetary moons, constellation guides, celestial orientation tools, and an interactive distance scale.
- Earth-focused sky views, an observer dome on Earth, and full-canvas planetary, orbital and stellar scale views.
- English and Arabic interfaces with kilometer and mile units.

Optional Celestial Spheres Pro unlocks all models and premium tools. Choose lifetime access for a one-time USD 24.99 purchase, or a USD 2.99 monthly subscription with a one-week free trial for eligible new subscribers. Local prices vary and are shown before purchase. The app contains no ads.

The monthly subscription automatically renews unless canceled at least 24 hours before the current period ends. After the free trial, the monthly price applies. Payment is charged to your Apple Account. Manage or cancel in your Apple Account subscription settings. Lifetime access is a separate, non-renewing purchase.

Celestial Spheres is an educational visualization. Historical-model distances and mechanisms represent their respective traditions; later discoveries and educational model extensions are identified in the app. Do not use the app for navigation, safety-critical decisions, or professional observation planning.

Copyright 2026 Celestial Spheres. All rights reserved. Third-party assets retain their respective licenses and credits in the app.

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