Top 10 iPhone Apps for Astronomers

It’s no great secret that I’m a big fan of geek toys. Some people may remember how amused I was by the iPod Touch I got a couple of years ago. Well ok, I finally bit the bullet and am now the proud owner of a iPhone (remarkably, this phone contract actually works out cheaper than my last one did). Seeing as it does everything my old iPod used to, and everything my crappy old Nokia phone used to, it’s pretty nifty having only one electronic gadget to carry around with me. The best part is, it’s actually a rather useful little tool for an astronomer to have.

It’s true that the line of “there’s an app for that” has become something of a joke. From Super Monkeyball to junkfood calorie calculators, there’s a lot of nonsense available on the Apple Store to run on your iPhone. Fortunately though, there are a lot of cool and useful things out there too.* These are 10 apps which may be useful to professional and amateur astronomers alike. Or just entertaining for bored undergrads down the pub…


Ever wonder what the Sun’s doing right now? In orbit around the lagrange L1 point between the Sun and Earth, SOHO is the SOlar and Heliospheric Observatory, constantly observing the Sun and sending images of it back to Earth. This handy little App will stream those images directly to your hand. Convenient if you were wondering when the next sunspots would appear.


Darkness is probably one of the best daylight calculators I’ve used. For any location on the planet, Darkness will calculate the Sun’s position in the sky, and give times for civil, nautical and astronomical twilights. It will also calculate the Moon’s phase and position in the sky, giving times for moonrise and moonset. Very useful if you need to make the best use of the dark.

Met Office

Weather can be the bane of many an astronomer’s life. I’ve joked in the past that I should give up astronomy and take up meteorology, and seriously, it’s amazing how much you learn about weather while you’re busy observing. For anyone based in the UK, this app gets data directly from the Met Office, giving up to date forecasts and satellite pictures.** Alternatively (and for anyone not in the UK), Weather Underground has a handy iPhone web app. All you need to do is point your browser to it.


Planets is a cool little planet compass. It calculates the visibilities of planets and shows their position in the sky. Ever find yourself wondering if that bright star is really a star? Have a glance at Planets. You may realise you’re actually looking at Jupiter!

a2z Pro

This one’s much more of a practical app. Formerly known as conversions, it’s a simple unit converter. It comes pre-loaded with several different things like temperature, length, speed and so on. Its beauty lies in the fact that you can define your own conversions. For instance, I spend a lot of time looking at quantum chemical calculations, and I’m forever having to convert units from electron volts to hartrees to nanometres. This app makes that much easier. Alternatively, create a new category for astronomical distances, and never find yourself wondering exactly how many parsecs 1550 light years is ever again.

Space WX

Going one step better than the Soho app, Space WX is a realtime stream of space weather. Everything you may need to know about the solar wind and activity, and the Earth’s magnetosphere and ionosphere can be handily checked from this app. The interface isn’t very polished, but there’s something rather cool about being able to see the current density of protons in the solar wind. Inline information tells you a bit about whatever data you’re looking at too, as well as where it comes from and why it’s useful. I’d love to say you would be able to use this app to find out about current solar activity disrupting communications, but in truth, if that were happening you’d probably just be getting frustrated about your phone not working.

Moon Globe

I would’ve killed for this thing when I was a kid, and it’s a must for anyone who wants to point a telescope at the Moon. Moon globe will show you names and information on every interesting feature on the Moon’s surface, including the location of the Apollo landers. Lets you view the Moon either as a rotatable globe, or face on, as you’d see it through a telescope. Incidentally, the same programmers have also released a Mars Globe…

Alpha Centaurii

A pocket almanac, Alpha Centaurii will give you information on the precise positions of all planets in the solar system for any given date. Perhaps more usefully, it has a date calculator, letting you view any time as Universal Time, Local Sidereal Time, or Julian date. Convenient for people like me, who forgot to note down the local sidereal time when observations were taken… It’s also a French app. But it’s not really a problem that the occasional bit of text is written in French, and by default it thinks you live in Paris…

Touch Term SSH

Yeah, ok, I’m a big geek. And the fact that if I’m bored on the bus, I can check how well my experiments are running on the supercomputer makes me happy. Seriously though, this is essentially a fully functioning SSH terminal. Whatever use you have for an SSH connection, this will do it.

Star Walk

Last, but by no means least… Star Walk has to be the prettiest iPhone app I’ve ever seen. An extremely capable piece of planetarium software, showing all the constellations, and more or less every visible star in the sky. For the planets, bright stars, and deep sky objects like nebulae, it also gives some interesting information. It even has a night mode, showing the screen in red so as not to damage your night vision. Star Walk was originally created last year as part of the International Year of Astronomy, and is one of the few apps which I actually paid more than 80p for, but it was definitely a worthwhile purchase. Though I’m still not sure about the crazy new age music they added in a recent update…

*Did I mention that, the next time I have a handful of hours to go before a deadline and I need to wait for a collaborator to e-mail me, the e-mail will go directly to my phone immediately? That fact alone is pretty much worth it’s weight in gold.

**The coolness of this managed to quell at least a little of my disappointment at not being able to see any perseids thanks to the cloud cover…

About Invader Xan

Molecular astrophysicist, usually found writing frenziedly, staring at the sky, or drinking mojitos.
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5 Responses to Top 10 iPhone Apps for Astronomers

  1. invaderxan says:

    I’ve had a couple of occasions now when hotel internet was… not as good as expected. That’s pretty much half the reason why I decided to get one of these little gadgets.
    Planets is actually pretty good, in that by default it only shows planets which are visible to the naked eye. If you want the locations of Uranus and Neptune, you need to flick a switch in the settings… :)
    You’re quite right that orbits at L1 are unstable. That’s the clever part! Celestial mechanics shows that because of the way the gravitational potential well works at L1 (also L2 and L3), an object can form a stable orbit around those lagrange points. The orbital axis needs to be perpendicular to the Sun-Earth axis though, to maintain the balance of forces, giving it the name ‘halo orbit.’

  2. invaderxan says:

    You’re welcome. I hope it was useful! :)
    And yeah, Alpha Centaurii seems to have disappeared, unfortunately. Which is a pity, because the date calculator alone is useful enough!
    Thanks for the suggestions too. I’ll be sure to have a glance at them when I can… :)

  3. 6_bleen_7 says:

    I run stuff on a Linux server all the time, so the SSH app would be a godsend, especially when I’m on vacation and the free wifi at the hotel proves to be not worth the price we paid (as happened a week ago).
    I once had to explain to someone using a planet-finding app (probably not Planets) that she couldn’t have seen Uranus and Neptune from a large city because Neptune is at the threshold of naked-eye visibility even under perfect conditions, and Neptune required a telescope under any conditions. If Planets explains under what conditions dimmer planets might be visible, that would be a major improvement.
    I’m curious: how does SOHO orbit the Earth-Sun L1 point without expending a lot of energy? L1 is a point of unstable equilibrium, is it not?

  4. Thank you for the list! I can’t seem to locate the Alpha Centaurii app, however
    Another set of good apps that I have
    3D Sun — feed from the Stereo and SDO space craft
    Exoplanet — I love watching the count of ‘Known Extrasolar Planets’ increment month by month

  5. sandalfon says:

    Wow, that sounds like such a great phone. So useful in tons of ways for those who really need it all.

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