Space Time
A free SkySafari alternative in your browser
SkySafari is the app a telescope owner reaches for, and it's very good. But its best features are paywalled twice, once per version and again as a yearly subscription. Space Time is a planetarium and a 3D universe in one, free, with no app and no account. It matches the paid Plus tier on most catalogs, and goes places SkySafari can't follow.
🚀 Try it now, nothing to install Free · No account · No subscription · Any modern browser
The honest comparison
SkySafari comes in paid tiers: Plus (about $30) and Pro (about $50, plus a $40–50/yr LiveSky Premium subscription for sync, the light-pollution map and weather). Here is how Space Time actually stacks up against both. We win some rows and lose some, and we'll tell you which.
| Capability | Space Time | SkySafari Plus | SkySafari Pro |
|---|---|---|---|
| Price | Free | ~$30 once | ~$50 + $40–50/yr |
| Runs in the browser, nothing to install | Yes | No, app | No, app |
| Same on every device, no per-platform repurchase | Yes | Buy per platform | Buy per platform |
| Planetarium sky for your location & time | Yes | Yes | Yes |
| Star catalog | 2.5 million (HYG + Tycho-2, Gaia DR3 distances) | 2.55 million | 29M + 109M Gaia |
| Deep-sky objects | 32,000+ (NGC/IC + Sharpless, Arp, Abell, more) | 32,537 | 784k + 3.4M galaxies |
| Comets (every known, searchable) | 4,000+ | 621 | 3,497 |
| Asteroids on real orbits | 7,700 | 5,112 | 746,410 |
| Moons | 187 | 38 | 187 |
| Live satellites + ISS passes (TLE + SGP4) | ~9,000 (full Celestrak) | 1,847 | 1,847 |
| Observing planner ranked for your site & night | Yes | No | Yes |
| Telescope & eyepiece field-of-view simulator | Yes | Yes | Yes |
| Fly the solar system in 3D, out to the cosmic web | Yes, five scales | Orbit Mode flyby | Orbit Mode flyby |
| Stand on the Moon, Mars, Venus or Mercury | Yes | No | No |
| Clickable named-feature atlas on those worlds | 4,600+ IAU features | No | Moon outlines only |
| Cinematic eclipses (totality, blood moon, umbra on globe) | Yes | Event finder | Event finder |
| Mission replays (Apollo, Voyager, New Horizons) | Yes | No | No |
| Shareable by link, embeddable in a page | Yes | No | No |
| Telescope / mount control (GoTo + push-to) | No, simulator + push-to HUD | No | Yes (Alpaca + INDI) |
| Camera control + plate solving | No | No | Yes |
| Cloud-synced observing lists & logs | One device only | One device | Yes (Premium) |
| Works fully offline | No | Yes | Yes |
What you get that SkySafari doesn't have
SkySafari shows you the sky from where you stand, then lets you orbit a textured planet from the outside. Space Time lets you go to the things you're looking at and walk around on them. Double-click Mars and fly there, then drop to the surface at Jezero Crater and look up at a Martian sky. Click any of 4,600+ named features across Mars, Mercury, Venus and the Moon. Watch the August 2026 eclipse's shadow cross the Atlantic from orbit, replay Apollo 11 from launch to landing, or keep zooming out past the Milky Way to 43,500 real galaxies. The planetarium and the spaceship are the same app, and it's free.
When SkySafari is the better choice
We'd rather tell you straight. If you drive a motorized mount at the eyepiece, do astrophotography with camera control and plate solving, need catalogs that reach 100 million stars and mag 18, want your observing logs synced across devices, or observe offline under a dark sky, buy SkySafari Pro. It's a mature, capable field tool and Space Time doesn't replace it for those jobs. Where Space Time competes is everywhere else: the browser, the phone, the classroom, the price, and every "what does the sky look like, and what is that thing" question that shouldn't cost a subscription.
FAQ
Is Space Time a good alternative to SkySafari?
For most people, yes, and it's free: a real planetarium that matches the paid Plus tier on most catalogs, plus a true 3D universe SkySafari doesn't attempt.
What does SkySafari Pro still do better?
Telescope and camera control, the deepest catalogs (109M stars, 746k asteroids), cloud-synced records, and offline use. For mount control at the eyepiece it's the right tool.
Is it really free?
Yes. No account, no download, no paid tier, and no subscription. SkySafari charges per version and puts sync and weather behind LiveSky Premium.
Can it control my telescope?
Not yet. It has an FOV simulator and a push-to finder that guides you by hand, but it doesn't drive a motorized mount.
Does it work offline?
Not yet. It needs a connection to load, then runs fully client-side.