Software : In Depth: How Linux is advancing astronomy

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In Depth: How Linux is advancing astronomy Posted: How Linux is advancing astronomy Go to any gathering of amateur astronomers and almost all of the computers on show will be running Windows, with a handful displaying applications such as Nebulosity and Starry Night on a Mac OS X system. While Macs are still the preferred option for media creation, Windows has a better selection of astronomy apps, such as Maxim DL, and wider driver support for cameras and charge-coupled devices (CCDs). PRO-GRADE: Telescopes in the Chilean desert Head into the professional world of astronomy, though, and Linux machines are ubiquitous. Speaking to science colleagues, fellow developers and reading this very magazine, it becomes clear that there are a wealth of options out there for avid stargazers and the same names and distros crop up again and again. Apart from astronomy software, the other key issue is driver support for telescope mounts and cameras. When it comes to commercial camera options, there are three approaches. The first, and probably cheapest, is using standard DSLR-type cameras, modified by removing the infrared blocking filter to increase sensitivity to night-sky objects such as faint emission nebula. These tend to give good wide-field views with telescopes, but suffer from a high level of noise when it comes to imaging. As you're typically exposing on an object for minutes at a time, building up over several hours or even days of exposure time, noise level is critical. Noise tends to look like speckles on the image, or an annoying glow in one or more corners (caused by thermal noise from the camera's electronics). The speckle is particularly bad, because the star fields look largely the same. Windows software such as Deep Sky Stacker or Maxim DL happily copes with this using calibration image frames. On Linux, Astrotack supports dark frame manipulation, and applications such as Siril can support the stacking of individual images. Controlling DSLRs in Linux starts with simple shutter/release and sensitivity control applications, which communicate to the camera via USB cables - the Canon EOS range is the most popular, because the cameras can easily be modified. You can then either transfer the images to the computer with a USB stick, or take out the CompactFlash (CF) card and insert it into a reader. Watch this space ROSETTA NEBULA: This picture of the Rosette Nebula, taken by the author, is typical of the types of deep sky images possible using modest home equipment With the second approach - using dedicated astronomical cameras rather than commercial DSLRs - the noise issue is less of a problem. These cameras connect directly via USB, GigE or FireWire to your computer, and usually have one or more stages of integrated cooling, which reduces the problems caused by thermal noise. The downside is that they generally have smaller fields of view, or when they don't they cost about 10 times more. When picking a camera, the monochrome flavour is usually more flexible with astro imaging, because it permits the use of the CCD with specialist narrow-band filters, which pick up specific frequencies of light emitted by things such as nebulae. It also has the side benefit of eliminating almost all light pollution caused by street lights. This is usually how deep sky imagers who live in suburban areas get their pictures. On Linux, serious astro cameras for deep sky imaging, by companies such as SBIG, QSI and Finger Lakes, are supported, with applications including GoQat for the QSI series also handling some of the pre-processing dark frame subtraction, as well as having integrated autoguider support. COOL OPERATOR: The Atik 383L+ cooled CCD camera, one of the most popular on the market An autoguider is a small camera that works alongside the deep sky imaging camera, and sends the telescope little corrections to its tracking systems to ensure you get pin-sharp stars. Telescopes usually track the sky in what's known as side-real tracking, which follows the motions of the stars across the sky as the Earth rotates, but even the more expensive telescope mounts have small errors. For visual use or short exposure use, this isn't a big problem, but when taking very long exposures it leads to unsharp and trailed star and object images. The autoguider effectively locks on to a star near where the main imaging camera is pointing, and keeps it locked in-between crosshairs. If the mount should move incorrectly, the camera picks this up and sends a command to the telescope mount to correct it. This is how 99% of all long exposure deep sky imaging is done, from the home observatory through to the Hubble Space Telescope. The third type of camera approach, typically for lunar, solar and planetary imaging, uses a high framerate webcam-type device to take a video of the object. The goal here again is to reduce noise, but mainly the effect of the atmospheric turbulence above us. With 100km of sky to punch through, large professional telescopes use adaptive optics lasers to measure this turbulence and send corrections to the telescope's mirrors. Adaptive optics is available in the amateur domain but it's expensive and only works with micro mirrors and no laser. For planetary and lunar imaging, the way most people beat the "seeing" (atmospheric mush) is to take hundreds of images in quick succession, as a video. Software combines these images, removing the ones where the seeing is not so good, and then composites the good frames to make one final sharp image. This is known professionally as "lucky" imaging, and while it was developed by professionals, the amateur community has taken to it far more. There is a lack of widespread driver support for CCD cameras in areas such as planetary and lunar imaging. However, companies such as Imaging Source and Lumenera, and firms that make the deep sky cameras we've already mentioned - SBIG, QSI and Finger Lakes - can or do provide Linux support for their products, and will, in many cases, assist with installation. If Linux is your platform of choice, check first that your camera is supported, though, because the deep sky ones mentioned are all quite expensive. When it comes to image post-processing, a few applications seem to be more popular than others on Linux. While their commercial Windows counterparts sometimes offer more options, these examples are no slouches. STAR TREKKING: DS9 is a popular image-processing application both in professional astronomy and education For image processing and data reduction there is the multi-platform DS9. It's used widely in educational projects, as well as at research facilities by people such as the Faulkes Telescope team. Handling Flexible Image Transport System (FITS) along with other file formats, it enables photometric analysis, basic image processing, histogram adjustment and image mosaic creation. DS9 is simple, but effective at what it does. It required a download of the source and then some command line compilation but, as with many of the applications, the clear online instructions made this pretty straightforward on our Ubuntu system. Dancing with the stars IMAGE MANIPULATION: SalsaJ is used in education to show students the ins and outs of image processing Again multi-platform, the Java-based image manipulation and processing tool SalsaJ is more comprehensive, and requires compiling and running initially from commandline interfaces. (There are software GUI-based tools that really help with this, but the command line approach is straightforward.) Widely used in education and available in multiple languages, SalsaJ also comes with online exercises for developing your astronomical skills, from measuring Doppler shift in exoplanets and looking at spectra, through to determining the weight of a galaxy. OLD FAITHFUL: Gimp is one of the most popular Linux applications, offering many of the facilities of Photoshop Gimp is hugely popular and sports a Photoshopstyle UI. It supports the FITS file format, commonly used in astro photography, along with dozens of others and the range of options will enable you to process images to a level as good as those offered by its commercial counterpart. (Albeit with a steep learning curve and acceptance that the UI is possibly not as intuitive as Photoshop's.) In terms of actual imaging acquisition, we've mentioned GoQat for the QSI range. Another popular application that supports both deep sky imaging cameras and the high framerate webcam approach is wxAstroCapture, which runs under Kubuntu, OpenSUSE and Ubuntu. Again, with clear instructions I was able to get this running with my Artemis cooled deep sky cameras. While their implementation for Windows of ASCOM-compliant autoguider support was not in the Linux version, preventing very long exposure photography, the user interface and level of control matched many of the features of my typical workflow software on Windows. With just a few extra tweaks to support autoguiders and the filter wheel (an Atik USB-controlled five-position wheel to change the types of filters my monochrome cameras use), I could have run an entire imaging session just in Linux. As an astro imager, I focus on deep sky objects and imaging comets, and this is something that many people with an interest in astronomy and computers fall for. You see those lush Hubble-type images in magazines, and Linux will pretty much enable you to achieve the same effects. Professional observatories such as the VLT, Keck and so on all have toolsets, which are sometimes freely available, so you can dive in at the deep end and look at the applications' professional use on a day-to-day basis. Being able to tap into the vast software resources of professional observatories should set you in good stead. It does take some work, research and effort to get many aspects of astronomy on Linux working and ticking over - for free and with the stability that professional astronomers crave - but the future for Linux is looking better than ever.

Tutorial: iTunes: the essential guide Posted: iTunes: the essential guide When Mac developer Casady & Greene sold its audio player, SoundJam MP, to Apple at the turn of the century, it couldn't possibly have imagined what would become of its poster child. Within a year it had been transformed into iTunes 1.0, then used as a launch pad for the very first iPod, and history was made. Today, iTunes is a true giant among Apple applications - a massive, multi-platform colossus that bestrides millions of Macs, PCs, iPhones, iPods and iPads. It has helped turn Apple into one of the world's largest entertainment retailers. And very soon it'll become an internet phenomenon too, thanks to the launch of iCloud and iTunes Connect - two new services due later this year and next, which will give you easy access to all the content you own, wherever you may be. Of course, iTunes has only been able to become ubiquitous because of what it can do. You can use it to buy, rent or download music, movies and TV shows; listen to podcasts or thousands of internet radio stations; buy books; subscribe to magazines; and keep your iOS device loaded up with tons of clever, innovative and exciting apps that will keep you entertained at home and away. And, of course, it's free. Indeed there's so much to iTunes that it can be tricky to know where to start, whether you are a new or experienced user. So we've put together this essential guide to help you get the best from iTunes, from the very basics to advanced tips and tricks, with particular emphasis on the key features of iTunes 10 and synchronising your stuff using an iPad, iPod or iPhone. Ready? Let's dive right in… What iTunes is, what it does and how it can benefit you… Because iTunes can do so much, it can seem daunting to use at first - there are so many options, tabs, sidebars and buttons to choose from. But when you break it down, it really is quite simple to get to grips with and you'll soon find yourself adding and enjoying content without a second thought. One of the best ways to figure out what's going on is to look at the Source sidebar on the left of the iTunes window. Here your iTunes library is divided into different sub-sections - Music, Films, TV Programmes, Podcasts, iTunes U, Apps, Ringtones and Radio - and it's where all your media content is organised. Below that is the Store section, which enables you to go shopping for new music, movies, and so on, using the iTunes Store, and to engage in some music-oriented social networking with Ping. And you'll also find Genius, which helps you discover old favourites and new media. And, finally there are Playlists, which gives you different ways to enjoy your stuff by slicing it up into manageable, customisable chunks. At the Source You can listen to or watch anything that's in your library using the Source sidebar. Selecting any one of the options reveals relevant content in the middle window (the browser). This is where you can see, explore and play all the stuff in your library. But what do you do if you can't find anything under Music or Films? You next step is to import or 'rip' content from media you own already, such as music CDs. The other option is to use your new iTunes account to do a little shopping at the iTunes Store. Importing a music CD couldn't be easier - it will automatically appear in iTunes when you insert one into your Mac's optical drive and iTunes will scurry off to the internet to fetch details about it from the Gracenote online music database. You can edit any details (these are known as ID tags or metatags) it finds by selecting a track or multiple tracks and selecting Command+I. You can also add in your own cover artwork either by scanning it in manually, doing a Google search or using the power of the iTunes Store. iTunes imports songs using the same audio codec as the iTunes Store - 256kbps AAC - although you can easily change this by selecting Preferences > Import Settings from the iTunes main menu. Here you'll find a wide range of audio codecs to choose from - including MP3, WAV and Apple Lossless, although iTunes doesn't support more exotic codecs like Ogg Vorbis or FLAC. To all but the most sensitive of ears, 256kbps AAC is virtually indistinguishable from CD quality and offers the best compromise between sound quality and storage space. Your mileage may vary. Album artwork To get album artwork from the iTunes Store you'll need to use either an existing Apple ID or an iTunes account (the two are usually interlinked); failing that, you'll have to create a new one. Do this by selecting Store > Create Account from the iTunes main menu. Once you've done that you can import album artwork by going to the main menu again and selecting Advanced > Get Album Artwork. Signing up for an iTunes Store account has several other benefits, of course: you can use it to buy and download a huge range of current and back-catalogue albums, music videos, books, movies and TV shows. You can also use your iTunes Store account to get a whole bunch of free stuff, from promotional singles and movie trailers to hundreds and hundreds of podcasts. You can even listen and watch study materials, courtesy of some of the world's leading universities, via iTunes U. Moving pictures Movie and TV content on iTunes is often available in both standard definition (640x480 resolution) and high definition (1280x720p) versions, with 1080p content rumoured to be available later this year. Watching HD content on the small screens of the iPhone or 11-inch MacBook Air may not be all that beneficial, but you can easily hook them up to an external monitor or a TV to make the most of the picture quality. Neither do you have to buy movies outright - the iTunes Store also gives you the option to rent a whole range of films. You can store a rented movie on your Mac for up to 30 days without watching it, but once you do, you only have 48 hours to watch the remainder otherwise it will magically disappear. Talking of the iPhone, we can't mention the features of iTunes without also including one of the main reasons why it exists at all: its close integration with iOS devices such as the iPhone, iPod and iPad. Setting up, managing and filling any of these devices with content is almost always done via iTunes, although that looks likely to change later this year with the introduction of iCloud. How to share your iTunes library Let your whole family in on the iTunes experience. Here's how… For those of you who have multiple users on your Mac, you'll notice that iTunes creates individual folders for each one in Home/Music. That's great if you'd rather not listen to your daughter's Glee soundtrack collection, but it's not so good if you want to share lots of stuff - music, movies, TV shows, and so on - because you could end up with gigabytes of duplicated content, a rapidly shrinking hard disk drive and a lot of wasted hours as everyone spends time on your Mac populating their own iTunes folders. The smart way around this is to create a shared iTunes folder that lives either in Your Mac/Users/Shared on an external hard drive that's connected to your Mac either physically using FireWire, USB or Thunderbolt cables, or wirelessly using Apple AirPort. Either way, everyone who uses your Mac can still have their own customised iTunes library - the only real difference is the way in which all of its media contents are stored. You can find out how to do this below in How to Share Music, Movies and More… Get organised The only tedious thing about merging an existing set of previously separate iTunes folders is that your new library will inevitably be filled with all kinds of nasties, from duplicated content to incorrectly tagged files with missing artwork. Your only option at this stage is to put in some hours trying to sort the whole mess out, but there are a few tools that can help you. You can track down the most obvious duplicates by going to File > Display Duplicates and then select which ones you'd like to delete, or you can use something smarter such as Dupin ($15/£9, Doug's Apps For iTunes, www.dougscripts.com), which gives you a higher degree of control over what's kept or deleted. You can also clean up dodgy file tags (artist name, album name, track name, and so on), either by selecting Advanced > Get Track Names from the iTunes menu bar (you'll need an internet connection for this to work) or to use something such as TuneUp (from $40/£25, TuneUpMedia, www.tuneupmedia.com), which uses audio fingerprint technology to identify songs, correctly label them and download artwork. You can also get artwork for your Media Library from the iTunes Store by selecting Advanced > Get Album Artwork. Other user accounts Once you're happy with the contents of your new tidy iTunes Media folder, you now need to do the same for each user account. The best way to do this is to go to File > Add To Library again, but this time select only the contents you want to add. That way, every member of your family will have the media they want - and you'll have an overview of the whole library so you can manage the contents. The only slight downer with iTunes here is that you'll periodically need to go through the Add To Library process again from time to time, since new content or changes made by other users of your Mac won't show up automatically when you open your own version of the iTunes library. Home Sharing Of course, if you have multiple Macs at home, sharing iTunes content between them becomes a whole different ballgame. You won't have to worry about duplicated content taking up space on your hard disk drive for one thing. But you can still share stuff between different Macs using Home Sharing, or you can just stream content from one Mac to another via Wi-Fi. To do either of these things go to iTunes > Preferences and then select the Sharing tab. To share music with other Macs in your household select Share my Library and then choose whether you want to share the whole thing, or just selected Playlists. If you want to, you can set a password that other users have to enter to get access to your library - something that can come in handy if you want to share a playlist of sweary comedy records with your partner, but not your kids. Home Sharing takes the concept one stage further by enabling you to copy the contents of your iTunes library between five different computers or devices using the same Apple ID. It's a great way to share the same content on a desktop Mac or a laptop at home, or even a computer at work. You can rate and change the play counts of songs in your library from another Mac - the only catch is, you can't share content between different Apple IDs, only the same ID five different times. For more details, see How to use Home Sharing below. As we've already hinted at in this feature, there may be some stuff in your iTunes Media that you simply don't want to share with younger family members, such as songs with explicit lyrics. This is where iTunes' Parental Controls come in. You can choose to restrict material by age range, rating, content (that is, whether or not it is labelled 'explicit') or even choose to switch off certain options altogether, including Podcasts, Radio, the iTunes Store and Shared Libraries. You can also manually tag specific tracks, albums and other content using third-party apps such as Subler (donationware, Damiano Galassi, http://code.google.com/publisher) or MetaX (free, Rodney O. Kerstetter, Kerstetter.net). How to share your music, movies and more 01. Share your Media library The best place for your new library is in a shared folder on your Mac or on an external disk drive. Select iTunes > Preferences > Advanced; click on the Change button to swap the default iTunes Media folder location from iTunes > Music > iTunes to its new destination. 02. Get and stay organised To make sure your files go and stay where they're supposed to select iTunes > Preferences > Advanced and choose Keep Media Folder Organised and Copy Files To iTunes Media Folder When Adding To Library. You'll need to do this for every user account. 03. Consolidate your library Now you can copy any existing media files to their new location. In iTunes, go to File > Library > Organise Library and then select Consolidate Files. You can also keep your iTunes Media files organised in categories by selecting Re-organise Files In The Folder 'iTunes Media'. How to use Home Sharing 01. Turn on Home Sharing Home Sharing makes it easy to share content from one Mac with up to five other Macs. But it only works if you have an Apple ID and use the same one to log into each Mac. To activate Home Sharing, select Advanced > Turn On Home Sharing from the iTunes menu bar. 02. See and share Home Sharing appears in the Source Bar in the main iTunes window. Listed below it are iTunes Media categories you can share between Macs. Selecting the Settings button enables each Mac to automatically be updated when you buy something from the iTunes Store. 03. Copying over content Once you've found a track, album or movie you want to copy from one Mac to another, select it and click on the Import button. You can update playlists and ratings in your master library by selecting the Home Sharing option in iTunes > Preferences > Sharing. Top 10 iTunes tips and tricks Discover the little things that make such a big difference 01. Edit song info iTunes makes it really easy to change the info about the songs and albums in your library at any time, simply by selecting the tracks you want to change and hitting Command+I. Do that and you get a pop-up window containing four different tabs - Info, Video, Sorting, Options. One of the most popular changes is to select Gapless Album under Options. This helps to prevent those annoying breaks between different tracks that are meant to seamlessly flow one into the other - ideal for both your favourite classical and prog-rock albums. 02. Restore iTunes 9's look and feel Apple introduced some interface changes with iTunes 10, the most controversial of which were ditching the colour icons on the Source sidebar, changing the 'traffic light' control buttons from horizontal to vertical and swapping out the old app icon with a new one. If you prefer iTunes 9's look and feel, then check out http://shaunr.net. Here you'll find a number of changes for iTunes 10 but make sure you back up iTunes before making any updates. 03. Control from your iPhone You don't have to sit at your Mac to control iTunes. Download Apple's Remote app (free) and take control of iTunes via Wi-Fi so you can play songs, watch movies and more wherever you are in your home. To get iTunes and Remote to work together, go to Advanced > Turn On Home Sharing from iTunes menu bar. Open the app on your iOS device and the two should pair. 04. Any requests? iTunes DJ is like a virtual radio station for your Mac, drawing music and other content at random from your library. You can even make song requests from another Mac or by using the Remote app for the iPhone and iPod touch. The songs you request then appear in the iTunes DJ playlist. You can decide how quickly your requested song plays by voting for it so it moves up the playlist. To set up guest requests and voting, go to iTunes DJ > Settings. 05. Create your own ringtone One way to personalise your iPhone is to use a custom ringtone. You can create your own using GarageBand '11, which includes an iPhone ringtone option. Or you could take a song from your iTunes library and turn it into a ringtone using an app such as iAm Ringtone Maker Lite (free, Mac App Store). The app enables you to select the bit of song you want and save it in iTunes in the Ringtones folder 06. Be smart about playlists Smart playlists are indeed very clever in iTunes. They enable you to create playlists that are based on certain rules - so you could have one that plays every single song by The Beatles except Yellow Submarine, for example, or another that includes 5-star songs only. Or both. Apple includes some great examples to get you started - you'll find them in iTunes' Source bar, but it's easy to create your own. Just go to File > New Smart Playlist and try out the various rules. It's fun and easy to do. 07. Get iOS apps automatically A feature of iCloud in iTunes 10.3 is the ability to automatically download purchases made on the iTunes Store using your Apple ID - so if you buy an app on your iPhone, it will download to your Mac. For now, you're limited to books and apps, but that will change when iCloud arrives in the autumn. 08. Stop iTunes file confusion iTunes can sometimes mix up audiobooks with music or put music vids in with movies. Changing file metatags in iTunes doesn't always work since files can revert to old behaviour if you have to reimport them. But you can make media metatags stick by using an app such as MetaX (free). 09. Discover hidden preferences There are lots of secret things you can do with iTunes 10 - add halfstar ratings or change orientation of the 'traffic light' control buttons, for example. You can access these preferences in one place with the Hidden Preferences app (free, http://dougscripts.com/itunes/). 10. Get free music It may not be pretty to look at, but the built-in Radio is one of the best things about iTunes. It enables you to listen to thousands of hours of music and chat from hundreds of internet radio stations. And it's all completely free. Radio categorises the radio streams for easy identification and you can easily tell what's currently playing. The only thing you can't do in iTunes is record the radio stream. But there are third-party apps around (Audio Hijack, £12, www.rogueamoeba.com, for instance) that enable you to do just that. Get the best from the iTunes Store and Ping Discover new music and find out what you're friends are listening to One of the best - and (whisper it) worst - things about iTunes is arguably the iTunes Store. It's great because it's a quick and convenient way to find, buy and download the latest albums, music videos, podcasts, books and movies. It's bad because you can spend a heck of a lot of money and arguably it's helping to speed the decline of bricks-and-mortar stores. iTunes 10 also introduces Ping, a quasi-social network that enables you to 'Like' and comment on songs you've listened to or bought and then share that information with friends and other Ping/iTunes Store users. To get the best from both services, of course, you'll need an Apple ID and to log your payment details with the iTunes Store. This enables you to make one-click purchases of media without having to enter your bank or credit card details each time. It also enables you to book a Season Pass for a TV series, each new episode being automatically delivered to your iTunes account when it's available for download. An Apple ID (essentially an iTunes Store account) is also necessary if you own an iPhone, iPod touch or iPad, as you won't be able to download any of those weird and wonderful iOS apps without one. The genius of Genius An Apple ID or iTunes account also enables you to use Genius - iTunes built-in recommendation engine. It's a great way to discover new music, movies and TV programmes based on content you already have in your iTunes library, as well as from other Genius users who have broadly similar tastes. To use Genius go to Store > Turn On Genius from the iTunes menu bar, enter your Apple ID, accept the terms and conditions and then select Turn On Genius from the next screen. Genius will then scan your iTunes Media folder for content and deliver its recommendations to you. You'll also notice the Source sidebar now has two new additions: Genius and Genius Mixes. Play any song from your library and then click on the Genius icon in the menu bar and Genius will automatically create a playlist based on your selection. The playlist can be as short as 25 songs or as long as 100. You can also refresh the playlist at any time for a different selection of songs or even save the playlist - a great way to save any Genius playlists you particularly like. Select Genius Mixes from the Source side and you'll immediately notice a grid of Genius playlists based on different musical categories. To play a Genius Mix simply select the playback controls at the centre of the Artwork. Unfortunately you can't customise a Genius Mix or even see what its contents are. But it's a great way to keep your music collection fresh - and throw up a surprise or two. The Genius is useful in another way, in that it enables Apple to make recommendations for you from the iTunes Store, based on what you like and others like already. You'll notice that the iTunes sidebar is populated with Genius Recommendations; clicking on the links here will take you to the relevant section of the iTunes Store so you can find out more or buy. To hear or see a preview of anything in the iTunes Store, hold the cursor over its track number and it will turn into a Play button, which will then serve up a 30-second clip for you to watch or listen to. Exploring the iTunes Store Select iTunes Store from the Sources sidebar in the iTunes browser and you'll be able to see the main categories of content that are on offer. It's a bit like discovering the floor map in a department store with Music, Films, TV Programmes, the App Store, Books, Podcasts, iTunes U and Ping available. Clicking on any one of these options will take you to a shop window for each section. On the right are various user account options and charts. The most important bit of the iTunes Store though is right at the top in the iTunes toolbar, where you'll notice that the Search field has now turned into Search Store. It's by far the quickest way to find anything specific in the store, with the results page returning everything related to the search term, from music to podcasts to apps. The easiest way to filter the result is to select one of the icons in the Filter By Media Type option in the search results sidebar on the left. Or you can also simply scroll down the page until you find the option you want. If you can't see what you want right away, clicking See All beside each Media Type opens up the field even more. If your favourite artists are on iTunes, it's easy to keep tabs on what they're up to and get warning of when new stuff from them comes to the store. Click on their name and you're usually taken to a customised artist homepage, which enables you to sign up for new alerts, to see their biography and the full range of the content available from them. If you've signed up to Ping, you'll also be able to 'Follow' them, and read any messages they've posted. Listed on the right sidebar under People you will find a list of fellow fans. Click on the See All option and iTunes will switch to a list showing them all. Beside each one you'll find a Follow button that enables you to follow them too. Following other fans might seem a bit weird, but it's a great way to discover new music: clicking on any fan's profile enables you to see what other kinds of music they like on iTunes. The chances are that if they like something you already like, you'll like the stuff that they like to. And if that involves a singer, a band, a style of music you've never tried before, it could open up whole musical avenues. If following random individuals on Ping seems a little stalkerish, then why not invite friends and family to join you too? You can ask people to join you on Ping by sending a message to their email address or by searching for friends using MobileMe, Windows Live, Yahoo or AOL - links to which are already built into iTunes. Linking Ping to your Twitter account is another great way to find out who else is around. It also gives you the option to automatically send a new tweet every time you do something on Ping, whether that's liking a posting or posting a review. Sync with your iPhone, iPod and iPad It's easy to share your content between your Mac and iOS device. Here's how… Ever since Apple launched the first iPod in 2001, it has been inextricably linked with iTunes - both as a way of filling it up with music and other content, and for managing settings and software updates. That largely remains true today with the iPhone, iPad and iPod touch, all of which are dependent on iTunes to a certain extent. However, the physical ties - hooking up your iOS device to a Mac or PC via FireWire or USB - that bind them to each other will be severed in September with the launch of iCloud, iTunes Connect and iOS 5, which will finally enable iOS and OS X devices to synchronise with each other wirelessly via the internet - no cable required. You won't even need to activate your new iPhone via iTunes as you do now. Having said that, being able to sync your iOS devices wirelessly won't always be either desirable or convenient, which is why iTunes on the Mac will continue to have a role for the foreseeable future. Whichever way you choose to sync your iOS device with your Mac, there are things you can do. Whichever iOS device you plug in, you'll see it appear in the Sources sidebar. Click on it and a new view opens up in the main browser window, which enables you decide what kind of content you want to sync, from address books contacts and emails to movies, music and podcasts. Along the bottom is a Capacity bar that tells you how much space on your device certain kinds of content take up. The first tab you come to - Summary - is arguably the most important. It tells you everything you need to know about your iOS device at a glance - from its name and storage capacity to the iOS software version it's running. The Summary table also enables you to update iOS or return the whole shebang to its factory settings - handy if your iOS device becomes corrupted for some reason or you just to want to clear it out before selling it on. Scroll to the bottom of the page and you'll come across Options, which includes a handy selection of settings you can toggle on and off so your iOS device behaves differently the next time you sync. These include the ability to sync only certain kinds of content, to live-convert higher bit rate songs in your Mac's iTunes library to 128kbps when you sync them with your iOS device, and to encrypt iTunes backups. Synchronising content Most of the other sections (music, films, TV programmes, podcasts and iTunes) work in a similar way. That is you can choose to synchronise the contents of each one of the areas automatically or manually (i.e. individually). The Automatic option works extremely well with a number of presets available that enable you to tweak at your leisure whatever content you want to get synchronised. You could choose to watch all the episodes of a certain show, the oldest unwatched episodes or the three latest episodes, for example. You can even customise these rules so they work differently for every iOS device that you want to sync. What you might not realise, however, is that you can also synchronise all kinds of other content between your Mac and your iOS device. And these are things that you may not have thought possible - hook up items such as your own photos, movies and music created using apps on your iPhone, iPod or iPad. In iTunes > Source sidebar > your iOS device, select the Apps tab at the top of the browser window, then scroll to the bottom of the page and you'll see the File Sharing option. The left pane shows all the applications you can synchronise files with; the right pane shows which files are being synced for each application. Get things together To synchronise a file, all you have to do is simply click on the application you want to sync, you can then drag and drop the file on to the right-hand pane. To finish off the sync, you then have to open the equivalent app on your iOS device and import it. Ideally, you'd be able to seamlessly make any changes to documents on one platform and see them reflected on the other, just as you can with Dropbox. Unfortunately, we're not there yet. Instead you have to manually copy the new version back using the steps outlined below. We're hoping that will change with the arrival of iCloud and iOS5 in the autumn. With iMovie, things become a little more complex. Projects created on iMovie for iPhone or iPad aren't compatible with iMovie for Mac, so you can't start working on a film project in one version and then finish it off with the other. However, you can partially get around this by importing unedited footage from your iPhone, iPad or iPod touch into iMovie on your Mac. And you can export a completed iMovie project created on your iPhone into iTunes. You can also transfer iMovie clips from your Mac to iMovie for iPhone or iPad using iTunes' File Sharing option, but you'll need to make them iOS-compatible first. The easiest way to do this is to add the clip you want to copy to a new project and then select Share > iTunes from the iMovie menu bar. In the drop-down window that appears, select which iOS devices you want to make your film clip compatible with and then select Publish. After a few minutes, an iOS-compatible version of your original film clip will appear in iTunes, under the Films tab. How to share Pages documents using iTunes 01. Get set to sync For this to work you will need to have Pages installed on your Mac and your iPhone or iPad. From the iTunes Source bar, select your iPhone or iPad and go to the Apps tab. Scroll to the bottom of the page until you get to File Sharing. Choose Pages from the left pane. The right pane will show the files that you can sync. 02. Drag, drop, transfer Find the Pages document you want to sync with your iOS device and then drag and drop it into the right File Sharing pane in iTunes. Open up Pages on your iOS device and tap the '+' icon from the menu bar. Select Copy From and then tap the iTunes icon. Your file will now be transferred. 03. From mobile to Mac To copy a document from Pages for iPhone to your Mac, open a document and then select the Tool icon from the menu bar. You'll now be presented with a range of options to choose from. Now go to Share and Print > Send to iTunes. The file is now available in iTunes on your Mac. How to get iOS apps organised in iTunes 01. Synchronise apps Synchronising iOS apps in iTunes is mainly painless except when iTunes decides to dump the apps you've chosen willy-nilly over several iOS screens. To tidy up, synchronise the apps you want on your iPhone or iPad first, then arrange them. Do it the other way and they'll just get messed up again. 02. Move your apps Now that's done it's time to sort them. It's quicker and easier to do this in iTunes if you can. Choosing and moving iOS apps works in a similar way in iTunes as it does on your iPhone or iPad. Click on the app you want to move to highlight it, then click and drag it to its new location. 03. Moving many You can group-move a bunch of apps by holding down the Command key as you click on each one. You can also create folders of iOS apps by dragging and dropping one onto another. Rinse and repeat until your files are organised. Now hit the Apply button again. There. All done.

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