Celestia vs Heavens-Above

Celestia is free, open-source software for visualizing space in 3D. It simulates objects ranging from planets and moons to star clusters and galaxies, which can be viewed from different positions in space and at different times. Solar system positions and movements are calculated in real time, and users can choose the rate of motion. Celestia also works as a planetarium: users can travel to celestial worlds, land on their surfaces, and see solar system objects in the sky. Add-ons expand the catalogues with objects, high-resolution textures, 3D models, spacecraft, and fictional objects. Celestia is licensed under the GNU General Public License and is available for Android, iOS, Linux, macOS, web, and Windows. The browser option is a lite version. Installation routes differ: Android versions are offered through Google Play, GitHub APK, and alternative markets; Apple versions are on the App Store, with a direct GitHub download for macOS. Windows users can use the Microsoft Store or sideload a GitHub version. The latest stable original-project release for Linux is listed as source code.

Heavens-Above provides satellite predictions and sky information through Android, iOS and web access. The website lists 10-day predictions for selected satellites, daily predictions for brighter satellites and Starlink passes from a launch. It also offers a live sky view, interactive sky chart, dynamic 3D Starlink orbit display and interactive 3D ISS visualization. Charts and information cover the Sun, Moon, planets, comets, asteroids and constellations. The Android app includes predictions for the ISS, visible satellites and radio satellites, plus orbit and ground-track views, night mode and an orientation-based tracker. Selected passes can be added to a device calendar. Predictions run locally, with a data connection needed every few days. The free plan costs nothing; Heavens-Above Pro costs $4.99, paid once and removes Android adverts. Predictions become less accurate farther from the current date.