Checking out JupiterMoons

Yesterday was a beautiful day in the Seattle area and the evening began mild and clear, so I decided to take a break from some work tasks, drag the telescope out to the deck, and have a few quick looks at Jupiter. It was also my first time to give a test drive to the new “JupiterMoons” iPhone app that I purchased from Sky & Telescope a couple of weeks ago.

The “Jupiter’s Moon” app for iPhone from Sky & Telescope
magazine shows you at a glance which of the planet’s Galilean
satellites is which, and also includes times for the day’s events
involving the moons and the Great Red Spot.

JupiterMoons doesn’t give away any secrets. You can get the same information from your favorite astronomy magazine or software package. In fact, S&T has Javascript utilities on its website that do the same things. But there are three advantages to the app that I can think of.

First, my iPhone is almost always in my pocket, so whenever I wonder what’s up with Jupiter the answer is handy. Second, on the app what you see is what you get. I always find those squiggly charts of Jupiter’s Galilean moons difficult to interpret, and usually have to take off my shoes to translate Universal Time into Pacific Standard. When you fire up JupiterMoons you get a snapshot of which moons are where right now and where you are. You can also look up times past and future. The view can be flipped or inverted to match the view in the gear with which you’re observing. Finally, the app is easy to read at night. There’s even a night mode that runs it in red light—not that we’re getting much in the way of night vision in our city backyards, but the feature may be important if you have a good, dark observing site.

A couple of other features are useful. Tap on the “events” button and you get a listing of the current day’s transits, eclipses, and occultations of the moons and their shadows, and transit times for the Great Red Spot as well. The “learn more” tab leads the user to some quick facts about Jupiter, Io, Europa, Ganymede, and Callisto.

Alas, there were no events going on during the short time I had for observing yesterday, save for the GRS being in view. But I was able to identify the moons, and JupiterMoons would have let me know if there was a double shadow transit or some other notable event coming up later in the night.

JupiterMoons is a great little app to enhance your impromptu viewing sessions. At $3 it’s a steal. It’s available for iPhone and iPad from the iTunes store.