JupiterMoons is your essential guide to observing the king of planets whenever Jupiter reigns over the night sky.

Sky & Telescope’s app helps you locate Jupiter’s four largest moons and time transits of the Great Red Spot with an easy-to-use interface. (The moons’ orbits are shown to scale with respect to Jupiter.) Plus, learn more about what makes these fascinating solar system denizens tick.

Observe Jupiter
• Locate Io, Europa, Ganymede, and Callisto at the specified date and time — unlike in Galileo’s day, they’re clearly labeled.
• Zoom in by tapping on the screen to better watch accurately timed Great Red Spot crossings and moon transits and eclipses. Or zoom out for a full view of the moons’ orbits.

Take Command
• Use the time controls to step through the seconds or hours, or speed through days or even years to see where the moons will be down the line.
• Customize your view to match what you see through your telescope.

Focus on the Details
• Click on any item in JupiterMoons’ complete events calendar to see the action. The calendar lists all the Jupiter-related happenings for the day: moon eclipses and transits, Great Red Spot transits, and moon-shadow transits.
• Learn more about Jupiter and its ice-and-fire moons with our encyclopedic descriptions, accompanied by spectacular images.

Please note: this application is designed to work in landscape orientation only so that you may view Jupiter, the Great Red Spot, and the Galilean satellites at their best.

What’s New

Version 1.1

- Update to Great Red Spot longitude calculation
- Minor bug fix in the "What's happening with Jupiter” events list
- Removed cross hairs around Jupiter
- Updated general design

Ratings and Reviews

3.8 out of 5
6 Ratings

6 Ratings

mnew67 ,

Wide Angle needs to be wider

The only knock on this app is that the wide-angle view does not allow sufficient room for Callisto much of the time.

skr213 ,

Decent - needs date/time control

This WOULD be a good app if it let you set your own time, rather than going off UT. Because that’s a 7 hour difference, when it gives me “today’s” events, it’s useless to me because technically anything I’m going to look at tonight is “tomorrow” according to the app. But you can’t switch to any date other than today on the “Events” page (if I’m wrong, please someone show me how!). You can move back and forth in time on the chart page, but not the event page, which is the page that would actually be useful for organizing my viewing.

gholt00 ,

NOT for iPhone X!

I love this app, but I can’t use it now that I have an iPhone X. Until they update this don’t try to use this with an iPhone X — you can’t get back out of it.

App Privacy

The developer, Guidebook Inc, has not provided details about its privacy practices and handling of data to Apple.

No Details Provided

The developer will be required to provide privacy details when they submit their next app update.


  • Family Sharing

    With Family Sharing set up, up to six family members can use this app.

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