First things first I completely blame Professor Brian Cox for my purchasing the iPhone App "Star Chart" for the sum total of £1.99. With his "Wonders of the Solar System/Universe" and "Star Gazing Live" malarkey he's only gone and got me all interested in all things science-y including astrophysics and, digressing somewhat, trying rather fruitlessly to understand the dynamics of quantum mechanics - if I die from an exploding head you'll all know why. Anyway, taking into account just how complex the subject of astronomy is, and perhaps maybe only on a superficial level, the "Star Chart" App is a wonderful supplementary tool for those learning about the arrangement of the nearby solar systems and galaxies.
What is it?
"Star Chart" effectively creates a map of the surrounding space up to a magnitude of +10.0 which in star terms will allow you to see and get information on up to a maximum of 116,567 of the nearest stars to Earth (considering there are between 10 sextillion and 1 septillion stars in the Universe that's not really that many). Within this map you can see planets, stars, constellations and any Messiers - these are a list of astronomical objects such as nebulas, globular clusters, supernova remnants etc which were first compiled by the French astronomer Charles Messier back in 1771 and "Star Chart" gives access to 110 of these objects. For each of these different points of interest you also get a pop up box which provides different information for each of the astronomical objects:
Distance from Earth/Sun in astronomical units (the approximate distance between the Earth and Sun); Diameter; App Mag (apparent magnitude - the brightness as seen by an observer on Earth); to determine the planet position the RA (right ascension) and DEC (declination); to work out the horizontal coordinates the current Azimuth and Altitude which are constantly changing.
The reference numbers for HD (Henry Draper catalogue) and Hip (Hipparcos catalogue) - both used for the spectroscopic classification of stars and the accurate measurement of the star positions; occasionally the Gliese catalogue reference number (looking at nearby stars within 25 parsecs (1 parsec = approx. 3.26 light years) of Earth); Distance from the Earth in light years; Spectral Class - analysing their light to determine their colour and size; Abs (absolute magnitude - measuring the intrinsic brightness) and App Mag; RA and DEC; Azimuth and Altitude.
Type of deep sky object; Messier No.; NGC reference number (New General Catalogue of Nebulae and Clusters of Stars); Distance from the Earth in light years; Diameter in light years; App Mag; RA and DEC; Azimuth and Altitude.
===How Does it Work?===
The map provided by "Star Chart" can be accessed in two different ways. One, you can begin looking at a stationary view of a chosen area of the sky (although movement of planets etc can be seen) and then just pan across in whatever direction you feel like with the scrolling of a finger or two, you can view the map in Augmented Reality mode which means you will see precisely what objects are located where your phone is pointing, so it doesn't just have to be in the visible sky, you can point your phone through into your neighbours' house or down towards Australia and still paint a picture of the night's sky. This AR mode works by using the GPS of your phone to locate your longitudinal and latitudinal position (in my case 51.41°N and 0.77°W) and from then on the application can generate a the real-time view of outer space using various sensory inputs such as your GPS, graphics or videos. You can set your GPS location manually if it doesn't seem to pick it up automatically but I suspect this may cause you problems as it is probably indicative that something isn't working if that is the case.
The first images you get can look quite cluttered as it covers quite a large area of space and you get lots of pretty looking atmosphere in amongst the black vacuum, labelled dots and constellation lines and constellation images which enable you to finally see how lines connecting seemingly random dots can actually resemble an archer or a giant bear or a giraffe and there is potentially some serious information overload here and for newcomers to astronomy such as myself, having any idea what you are actually looking at is challenging enough. Thankfully, this App provides a very effective search facility that allows you to search for planets, stars, constellations and messiers either alphabetically or through a search engine. In Non-AR mode you will instantly be taken to or very close to the location and the information box about your chosen object pops up, and in AR mode you will get a big white arrow pointing you in the direction and you can move your phone around until you find it and you'll know when you have as the arrow disappears and once again the information box is displayed. However, in AR mode it is quite difficult to remain in one location as keeping your arms steady requires the training of a Zen master so if you are looking for something specific rather than browsing around I'd recommend not using AR.
This App also offers a zooming feature so you can increase the magnitude of whatever object you are looking at and have a better look at it, which is particularly good for close planets and things like galaxies and nebulae which can look very attractive and in the world of Professor Brian Cox beautiful. I would recommend doing this in non-AR mode though because in AR mode once you start zooming in even the slightest movement of micro-millimetres can take you light years away from where you want to be pointing and finding your object again can be both frustrating and make you feel sea sick! In non-AR mode the picture remains stable and you can scroll easily to refocus on your object if it flies off unexpectedly from view due to its natural movement across the sky. There is a limit to how much zoom you can achieve and whilst you can zoom in nicely on the Sun, the Moon and the nearest planets to Earth in our solar system, and quite a lot of the messiers, but I had a look at Proxima Centauri, our closest star, and that just remained a yellow dot so really you can only benefit from the zoom on nearby or scarily massive objects. You can also change the date you are looking at the sky with for either the day, month of year to see how the objects move in an area of space all the way up to the year 9999 so it is possible to see into the future! This is quite fun as you can see things like planets flying around the faster you move through time and I'm sure there is some scientific benefit here also for predictions and such the like.
You can customize your "Star Chart" just the way you want under the settings category which allow you to turn things such as the atmosphere, constellation lines/images/Latin names and star/planet/constellation/messier labels on and off, change the units of measurement from metric to imperial and light years to parsecs and vice versa, choosing to display distances in Astronomical Units (AU) or not and adjusting the magnitude of stars to display from +6 up to +10. If you choose +6 only 5017 stars will be displayed and up to +10 116,567 will be available, but the performance of the app can be severely compromised by selecting these higher magnitudes as the images are much slower to load and move around which kills the flow noticeably and makes manoeuvring around much more frustrating .
There is also a Night Mode available which basically turns everything red. I'm not sure of the point of this as it makes everything quite hard to look at and I tried standing in the freezing cold of night in my pyjamas just the other day to see what the normal mode looked like and it was absolutely fine in my opinion. The app also provides an online support page giving basic tips for any AR or GPS issues and what to do if your compass goes doolally which involves pretty much twiddling your phone about in a figure of 8 - if only computers could be fixed in the same way. They also provide an email address if common sense can't solve any problems although in my many months of using this App I have had practically zero issues, the only ones actually being interference with the compass and I can confirm, whilst somewhat embarrassing, wildly swinging your phone in a figure of 8 does indeed solve the problem.
===Star Trekking across the Universe===
For the meagre sum of £1.99 this is a stunning and well produced App which any fan of astronomy would probably thoroughly enjoy. There are some wonderful features such as the use of Augmented Reality to be able to see fascinating astronomical objects in real time anywhere in (relatively) nearby space from simply swivelling on the spot or to alternatively view specific stationary segments of space thus avoiding flying haphazardly all over the place and giving yourself motion sickness when searching for something specific in AR mode. Searching, zooming through space and time and customisation are extra benefits which enhance your viewing experience and you do get some useful, if not sadly scant, information on each object of interest but the reality is you are never really going to expand your knowledge of astronomy a great deal with what is provided, although perhaps you can gain a better understanding of the arrangement of the stars, so I would say this is just a fun, and useful supplementary tool for those with an interest in astronomy, but recommended nonetheless.