Space Time
A free Stellarium alternative in your browser
Space Time and Stellarium both draw the sky for your location and time. Space Time also lets you leave the ground, visit planets and spacecraft, and continue out to the Milky Way and nearby galaxies.
🚀 Try it now, nothing to install Free · No account · Runs in any modern browser
Feature comparison
Stellarium Web and the desktop application have different feature sets, so the table compares them separately with Space Time.
| Capability | Space Time | Stellarium Web | Stellarium (desktop) |
|---|---|---|---|
| Runs in the browser, nothing to install | Yes | Yes | No, install |
| Planetarium sky for your location & time | Yes | Yes | Yes |
| Leave the ground: fly the solar system in 3D | Yes | No | No |
| Continuous zoom out to the Milky Way & cosmic web | Yes | No | No |
| Stand on the Moon or Mars and look up | Yes | No | Sky only, via location |
| Spacecraft on real JPL trajectories, Apollo replays | Yes | No | No |
| Watch a solar eclipse from space (umbra on Earth) | Yes | No | No |
| Observing planner ranked for your site & night | Yes | No | Limited |
| ISS & satellite pass predictions (TLE + SGP4) | Yes | No | Plugin |
| Telescope & eyepiece field-of-view simulator | Yes | No | Oculars plugin |
| Star catalog depth | 2.5 million (HYG + Tycho-2; Gaia DR3 distances; click any star) | Online surveys | Up to hundreds of millions |
| Telescope / mount control | No | No | Yes |
| Works fully offline | No | No | Yes |
| Plugins & scripting | No | No | Yes |
| Price | Free | Free | Free, open source |
What you get that Stellarium doesn't have
Space Time adds free 3D movement beyond the ground-based sky. Visit Jupiter, replay the Shoemaker-Levy 9 impacts, follow Parker Solar Probe, replay Apollo 11, or view an eclipse from orbit.
When Stellarium is the better choice
Desktop Stellarium is the better fit for mount control, very deep star catalogs, offline use, plugins, and scripting. Space Time is aimed at browser use, phones, classrooms, observing plans, and 3D exploration.
FAQ
Is Space Time a good alternative to Stellarium?
For browser use, yes: a real planetarium with a catalog that reaches 2.5 million stars, plus 3D flight Stellarium doesn't attempt.
What does desktop Stellarium still do better?
Telescope control, deeper catalogs, offline use, plugins. For mount control from a field laptop it remains the right tool.
Is it really free?
Yes. No account, no download, no paid tier.
Does it work offline?
Not yet. It needs a connection to load, then runs fully client-side.