Stellarium is a well-known name to astronomy buffs that have long used the open-source program on Windows, Mac, or Linux desktops. Stellarium Mobile (for iPad), created by two of the developers of the desktop versions of Stellarium, brings the program to your iOS device. Though it loses a few features, it retains the program’s beautiful, and for the most part realistic-looking, depiction of the heavens.
I tested Stellarium Mobile with an iPad Air, though it’s also usable on an iPhone. When you open the app, you’re presented with a view of the sky. In daytime, when it’s unsure of your location or in what direction you’re facing, it fast-forwards the time to the evening to show the night sky; otherwise it shows the sky at the current hour. In daylight, unlike some programs that still show a star-filled sky, Stellarium only shows the objects you can see in daylight (the Sun, the Moon, and Venus). Stellarium does a very good job in depicting the changing light of twilight.
The night-sky view is also appealing and—for the most part—realistic looking. Pointing your iPad at the sky will reveal the stars or planets visible in that direction. You can pinch or stretch the screen for wide-field or zoom views, or use the plus and minus buttons at the bottom of the screen.
At the lower left is a clock showing the date and time, down to the second. Tapping the time enlarges it and brings up four arrow keys; if I had to label them I’d call them Backward, Play, Forward, and Hourglass. Backward makes time run backwards, and each time you tap the arrow, it speeds up the rate of time by an order of magnitude. Likewise, Forward lets you move forward in time at hyper-speed, and watch the motion of the stars over the course of a night, then the arrival of the day, followed by another night, etc. The Play arrow returns time to its normal rate of passage, and the Hourglass arrow returns you to the present.
You can also make time pass backward or forward—and watch the stars move across the sky—by dragging your finger across the screen. I found the time controls tricky to master and sometimes nonresponsive—returning to the present was harder that it should have been. Perhaps this is a lesson to would-be time travelers.
At the screen’s upper left are a down-arrow, a circle with a star in it, and the designation (such as “HIP 32012″) for the star closest to the position where you last tapped the screen. A little circle in the sky view will reveal the position of that star. Tapping the down arrow will morph it into an up arrow, and reveal some basic information about the star: its magnitude (apparent brightness) location in both celestial and altitude/azimuth coordinates, and distance in light-years. While this information is useful, it pales in comparison with the comprehensive data (and descriptive info, for brighter objects) you can access on each object you tap on in SkySafari 3 (for iPad), for instance.
Some objects like the Orion Nebula look gorgeous and realistic when you zoom in on them; others are less impressive. While the Pleiades look good from a distance, with a hint of their nebulosity visible, in a close-up view they just appear out of focus and muddled. Planets do not appear as bright, relative to bright stars, as they do in reality. When you close in on a planet such as Jupiter, you can see its disk and moons, although when I got too close it looked washed out.
A Dozen Toggle Icons
At the screen’s bottom right is a gear icon that reveals a new set of controls: 12 icons. All are “toggles”: they either turn a feature on, or off. (When the feature is on, the icon is lit up.) One enables/disables constellation lines; one adds or removes constellation labels. An icon showing a figure with a star as his head enables or disables illustrations depicting the classical constellation figures—gorgeous but distracting if you’re trying to find your way around the sky. There are icons for the equatorial grid, showing celestial coordinates, and the azimuthal grid. The Ground icon can remove the ground, revealing the entire sphere of the heavens. You can enable or disable the Atmosphere, showing horizon glow, for example. Another icon shows the cardinal directions, another adds labels to stars and one to nebulae (and other deep-sky objects such as star clusters and galaxies). Sensors Control will realign your iPad with the view of the stars beyond it. The Night View icon turns all items on the screen red to preserve your eyes’ dark adaptation.
When the 12 icons are visible, you’ll also see Search and Settings icons at the left edge of the screen. From Search, you can type in the name of a star, planet, or other object. Although a few bright asteroids are included, there aren’t any comets. It also doesn’t display artificial satellites, like some planetarium apps. The Settings section lets you change the location and time, and tells you a little bit about star lore from many different cultures. You can switch your Earthly landscape between several options, and change some settings related to the display of planets. Although it has some good information, it’s no substitute for a Help section, which the app doesn’t include.
Trapped in a Black Hole
I encountered one serious if intriguing operational glitch. For a while I found myself trapped in what I call the “black hole view” in which the center of the screen showed a black disk—actually, the bulk of the Earth itself—with the stars and constellations encircling it at the edge of the screen. Instead of looking up, in effect I was looking down, in a fisheye view. I have no idea how I got into that view, and the only way I found to return to normal view was to close the app, turn off my iPad, turn it back on, and relaunch the app.
Stellarium Mobile is one of the better iPad astronomy apps, though it doesn’t come close to our Editors’ Choice, SkySafari 3 (for iPad). That app provides much more information about the stars depicted, has a much larger database of asteroids, and includes many comets as well. I didn’t find Stellarium easy to navigate in, and encountered several snafus. That said, Stellarium provides a visually stunning and—for the most part—realistic looking depiction of the night sky, showing more stars than most other planetarium apps at about its price, including SkySafari.
Copyright © 2012 Ziff Davis, Inc