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2,862 Tutorials

How to use Stellarium: free astronomy software for your PC

Use your PC or laptop to make sense of the night sky

If you’ve ever gazed up at the sky on a dark clear night and been mesmerised by the sheer number of stars you’re not alone in finding the heavens fascinating. However, for many, that initial wow factor is often followed up by a desire to know a bit more about all those tiny dots of light.

While that quest for knowledge might not go as far as wanting to know the difference between a white dwarf and a red giant or between an elliptical and a spiral galaxy, many people like to have at least an inkling of what they’re looking at. See also: Best iPhone apps: Five free apps for astronomy

Here we investigate some software that will provide you with that information and so make your sky gazing experience all the more satisfying. What’s more, in addition to identifying the various stars and planets in the sky, these applications will also help you to observe something you’ve been hankering to see. So, for example, if you want to take a look at Jupiter, you’ll be able to find out when to look for it and in which direction to cast your gaze.

See also: Best Android apps: Five free apps for astronomy

One of our favourite packages is Stellarium which is available for Windows, Mac OS X and Linux – it’s totally free and can be downloaded from www.stellarium.org. In many ways it works in just the same way as the large scale planetariums like the one at the Royal Observatory in Greenwich.

In other words it can display the sky as it would look from any place on the Earth’s surface for any time, past, present or future. However, whereas a public planetarium displays the image on the domed roof of the auditorium, Stellarium shows the sky on your PC's screen.

If you have a laptop, you can take it outside to view the sky at night. Alternatively you can print out a sky map to assist you in identifying the various heavenly objects. What’s more, you can search for any astronomical object and, if it’s not currently visible or it’s still daylight, you can fast forward to find out when you’ll next be able to see it.

You can also use a smartphone or tablet as a portable planetarium. In some ways these apps aren’t as fully featured as PC software but, because some smartphones and tablets contain gyroscopic sensors, you only have to point your device in a particular direction for it to display the scene exactly as you’d see it straight ahead.

You might also be interested in Google Sky. Most serious astronomers reckon that Stellarium is better as a planetarium package but for viewing impressive space imagery from the Hubble Space Telescope, for example, Google Sky is pretty nifty. What's more, in addition to seeing astronomical objects in visible light, you can also view them in ultraviolet and X-rays.

How to use Stellarium

1. When it’s dark, start Stellarium. Move the pointer to the left edge of the screen in the bottom half to display the left toolbar and click on the top icon (“Location window”). Select a nearby town from the extensive list in the top-right or, better still, enter your latitude and longitude. Enter a descriptive name for your location against “Name/Town” and select “Use as default” before closing the Location dialog box.

Stellarium 1

2. Select the third icon on the left toolbar (“Sky and viewing options window”). Try out the various options on the Sky and Markings tabs which dictate what’s displayed and what’s labelled but don’t deselect “Cardinal points”. Note that in addition to showing labelling for stars and planets you can also see constellations. Try out the sliders on the Sky tab that specifies how bright something has to be before it’s labelled.

Stellarium 2

3. Initially your view will be looking South as indicated by the red letter “S”. Look elsewhere by dragging left, right, up or down. If you’re using Stellarium on a laptop outside, select the “Night mode” icon from the bottom toolbar (names appear as you hover over the icons). This causes the display to appear in red on black so your eyes aren’t desensitised.

Stellarium 3 - night mode

4. Now try searching for something that isn’t currently visible. Select the fourth icon from the left menu (“Search window”). On the Object tab, enter the name of an object (e.g. Saturn, Jupiter, Venus, Moon, Andromeda) and click on the search icon. The display will rotate until the object is centred and a marker will identify it. An object might not be visible because it’s hidden by the Earth.

Stellarium 4

5. If something you searched for isn’t visible, you could try fast forwarding to see if it’ll appear anytime soon. “Increase time speed” and “Decrease time speed” icons are in the bottom toolbar as is a “Set normal time rate” icon which will cause time to proceed at its normal speed or pause it. Note also the “Set time to now” icon which returns the display to the current time and date.

Stellarium 5

6. Finally you can see how some objects can be viewed in more detail than you’d achieve with even the biggest Earth-based telescope. Make sure Saturn is visible on screen, select it by clicking on it, and then select the “Centre on selected object” icon in the bottom toolbar. Repeatedly tap the Page Up key until you see the planet in all its glory, moons and all.

Stellarium 6

Next page: Astronomy apps

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