University Lowbrow Astronomers

The iPhone & Astronomy.

by Krishna Rao, MD
Printed in Reflections: June, 2009.


Greetings, friends! I’ve been a Lowbrow for 3 years now and it’s about time I wrote an article! I’ve been playing around with the various astronomy applications for the iPhone since the App Store opened up last summer. For those of you who have one or used one, you’ve probably realized that the mobile computing platform of the iPhone clearly has great potential to be a useful tool out in the field. Maybe this is why 3 astronomy applications joined the many others in the App Store as “inaugural” applications, launched with great pride by Apple. A year later, there are at least 10 astronomy-related iPhone apps out now, from full, professional-grade star chart programs to red flashlight apps, and the “inaugural” apps have been tweaked many times over with updates, for the better. I’m going to review two of these applications briefly below, StarmapPro (a “light” version is also available, but the pro is only $7 more, so why get the other one?) and Star Walk (the official International Year of Astronomy application). I will not comment on two other decent apps, GoSkyWatch and Distant Suns, as I don’t really recommend them for folks like us or laypeople as they fall short of both needs compared to the others (but GoSkyWatch is a close “3rd”). My reviews are based on the iPhone 3G, but I don’t see why this wouldn’t apply to the first gen iPhone, or even the iPod touch, for that matter. First, however, a few preparatory guidelines.

Tricking out the iPhone for Astronomy

Although all of the iPhone astronomy apps include a night vision mode, you’ll quickly find that’s not good enough. Firstly, some of them don’t implement it well or fully (Distant Suns, for example, does a particularly pathetic job) and secondly, even in full, programatically well-implemented night mode the iPhone itself has a very bluish screen with a lot of off-axis blue/white color leakage. This is even apparent in the red flashlight apps! This is obviously unacceptable for field use when pursuing those faint fuzzies, so the first task is to create a red transparent filter for the screen. The red plastic can be obtained in various ways. You can purchase it at an arts supply store, go to Kinkos (or on your printer at home) and get a transparency printed in red (RGB: 255, 0, 0), or buy a few sheets from (in this economy, that may be a nice thing to do since I’m sure they need the support). Actually affixing the plastic to the screen is easiest if you’ve got a case. I’ve cut mine to be easily slipped in or out of the hard case I’ve got protecting the iPhone. Acceptable cases for this purpose usually run about $30. My favorite is the line from Agent18 (, as they come with a docking adapter and are easily taken on and off and are also extremely thin and lightweight while still being protective (yes, I realize I sound like a commercial; no, I don’t own their stock), This will dim the scattered blue/white light of the iPhone enough to be useable, in conjunction with the night vision mode in your apps. The one last trick is to make the unlock screen night friendly as well. The iPhone will slip into sleep mode every few minutes when not used and to get back into the program you were in, you first have to “slide to unlock” on the unlock screen. This screen displays a background image of your choosing, plus bright white icons and text. Although you can’t fully turn this screen into night vision mode, you can at least use a blank, red background image which, used with the red plastic filter you’ve fashioned, is good enough. I usually still point the screen away from me when unlocking just to prevent the glare. Finally, you’ll have to manually set the appropriate brightness level of the display. There is no one-size-fits-all setting I can recommend, since this varies depending on the program and the darkness of the specific plastic filter you fasioned above, but half-way works for my setup just fine. If you don’t do this, the iPhone auto-adjusts the brightness and will likely pick a too-dim setting when you’re in the field.



This is a fantastic application. It has many extremely useful features, a very thorough object database and star catalogue, and is easy to use after spending 5 minutes reading the manual. Over the past year, the developer has been very responsive to comments from reviewers in the App Store, and has really improved the already brilliant program. I’ll breakdown and review the features:

Main screen:

Intuitive point, pinch and zoom interface that is smooth and without significant or annoying lags. The location, date, and time are automatically set using the iPhone GPS, but you can easily change these manually. There many customizable options: show/hide the horizon, show/hide object/constellation labels, overlay a telrad (my favorite feature by far), include cardinal direction labels, show/hide ecliptic/alt-az/equatorial grid, show/hide variable and double star icons, change limiting magnitude of stars displayed (default is down to 16!), and the list goes on and on. No other iPhone app even comes close to the level of customization here. A particularly nifty feature is the eyepiece view, which when entering your telescope and eyepiece details, can show you a properly oriented FOV. You can swap between this and the regular view by flipping the phone over and back (the iPhone has a built-in accelerometer). Very cool.

Object Search:

You can do this in many different ways. The standard options are all there: search by object type (planets, stars, galaxies, clusters, nebulae, catalogues—messier, NGC, IC included, or just browse the main screen. An amazing number of objects will show up, depending on your zoom level, on the main screen so you can easily browse by region of the sky.

Object Info:

Very thorough. Most common objects have pictures associated with them and the usual data about magnitude, size, etc. Full ephemeris data is also present with rise/set times and position graphically displayed on a background indicating when the sky is dark. If you’re near an internet connection (or have edge / 3G activated) you can hit a button to get even more info beamed into your phone on demand. From this screen, you can also hit the “find” button and get to the object by following the arrow (and even see the telrad overlay, if that option is selected).

“Tonight” feature:

This is another great part of the app and very useful for planning observing sessions. On an overlay of the time with darkness indicated, the objects of interest for the observing night are displayed. You can apply useful filters such as “naked eye,” “telescope,” “galaxies,” etc. You can also sort by rise time, magnitude, or only display the circumpolar ones. From this screen, objects can be chosen and added to the “featured” section, so you can create a personalized list and just jump to this section when ready to observe.

There are many other features in this app including the ability to control a telescope, a logbook, a photographic logbook, that I haven’t used so won’t go into, but hopefully you can start to see why I’m so enthusiastically endorsing it! For $19, it’s a steal!

Star Walk

($5—itunes link: )

The official IYA 2009 iPhone product is a great application for enthusiasts and layfolk alike. It is not nearly as feature-rich or powerful as StarmapPro, but it gets the job done for casual sessions with binocs or naked eyes.

Main Screen:

As above, it can use the iPhone’s location feature to find your position, date, and time, but you can manually change this. It is also a fluid, intuitive, point, pinch, and zoom interface common to all iPhone apps. Unlike other apps, this one can only be used in landscape mode, which is not a huge limitation but can be a little more cumbersome if you’ve got thick fingers and clumsy hands like me. The visual display is quite beautiful, with a fairly photorealistic sky and a few tuning options for labels and such. The night mode is complete and useable.

Object Search:

Can find stars, solar system objects, and the messier catalogue. That’s about it, but remember this is designed for the public.

Info Screen:

Select an object and hit the info button to bring up useful info about the magnitude, distance/mass/etc., displayed in an entertaining way with sound effects. It includes pictures for many objects as well and the polished interface garnered many “oohs” and “ahs” the last time I used it, which was our on-campus collaboration with the student club.

Overall, I think this is a great app to have on hand during our public events to pull up quick facts on objects and give people an idea of what the object they’re seeing looks like before peeking in the scope. When my non-astronomy friends ask me about a good astronomy app to pick up, this is the one I tell them to reach for.


Overall, I’m happy with the astronomy offerings on the iPhone. That being said, there is always room for improvement but as long as the developers above keep supporting their programs, things are only going to get better. You do have to do a little initial ground work to make your phone usable in the field, but trust me, it’s worth the investment. Now who wants to bet after reading this that John Causland will be the first of you to go out and buy an iPhone!


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This page originally appeared in Reflections of the University Lowbrow Astronomers (the club newsletter).
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