Caoimhín's Content

Today, we are going to have a quick look at Stellarium. Stellarium is the software that I use for these videos, and it’s free. It’s available online and regularly updated. I just updated it, so I am currently using the latest stable version of the software, Stellarium 24.2. You can download it from stellarium.org. The software works on basically everything, Linus, MacOS, Windows, and various architectures. There are various formats that you can download it in and there is a web version so you don’t have to download anything at all to use a simplified version. Not only is it free, it’s open-source so you can make changes to it yourself. There’s a whole community where scripts, custom landscapes and various plug-ins are shared, along with advice. You can donate to the community, but it is optional. If you want to then you can just download it and try it out, which I recommend as it is a lot of fun.

I have updated to the latest version to talk through some of the features, just in case anything has changed. After downloading and launching Stellarium, I recommend moving your mouse cursor to the left edge of the window, to bring up one of the trays. This is a set of icons leading to menus, including a help menu marked with a question mark. This will bring up a window with icons for sub-menus along the top. One of these is a list of hotkeys, one of the most important things for me and my usage of the program. Not only is there a list of the of the different hotkey functions, you can also change the key bindings if you need something that’s more suitable for you. A lot of the hotkeys involve using the mouse wheel, but you can do with a lot of these things just using the trackpad on a laptop as well, which is what I do. There’ are loads of hotkey functions, loads and loads of them, many of which I don’t even use. However, the few hotkeys I do use are very useful, such as the options for controlling time. Particularly, L is used to move time forward faster and faster, or slow down how quickly time is moving backwards. J is used to slow down the speed if you are moving forward, or to reverse it faster and faster. K will bring time back to running at the speed it normally does, one second per second forward. As well as the hotkeys, if you bring your mouse cursor down to the bottom edge of the window, another tray will come up. This tray includes a rewind, fast forward and pause or play symbol. These function like L, J and K, but you can click the pause button to actually freeze time, which can be useful. There is another symbol between the pause and fast forward that brings the time back to the “present”, what ever that is for your computer or settings.

When you start up Stellarium for the first time, it will assume some default starting location. I’m not sure where that default location is anymore. I’ve been using Stellarium for nearly a decade and I always change the default location to Cork, and this is inherited by updates. Luckily, this is something you can do, you can change the default location to anywhere in the world. The location window is in the side tray, near the top. The map window this brings up looks nicer, clearer and more detailed than it did before the update, which is nice. Details as small as Hawai’i are now visible, which I don’t think I was the case previously. Once you’ve picked a location, you can use the setting menu, the wrench icon on the side tray, to set the new location as the default location.

The default settings can cover quite a lot, whatever the level of light pollution is, what height you are at and landscape you want to use. You can also set the default field of view, what direction you are looking, all of those things can put in as defaults. Also on the bottom tray are several other icons with useful features. From the left, there are a few option for the constellations. These icons also have associated hotkeys that serve the same function. I don’t usually use the hotkey C to bring up the lines of the constellations, I just go down to the tray and click the icon. There’s another for the names of the constellations, then the art of those constellations. One hotkey I do know is B for the boundaries between those constellations, as this doesn’t have an associated icon. The boundaries in particular, along with the art and lines, look extra clear, so I’d say there has certainly been a few cosmetic changes in this update as well. This is of course along with new objects and other features. There are also couple of the icons for grids, the equatorial grid and the azimuthal grid. I don’t use those much, but you can see me use them in my video about the analemma, attached to the associated article on this website.

There are also icons to remove the atmosphere and the landscape, of course I use those all of the time. There is also one for the cardinal points, so you can turn off the markers for the compass directions along the horizon. I generally like to keep them up, to help me keep track of what direction I’m looking. Then are the planet labels, and it’s usually clear if this is on, as it will label the Moon, asteroids and other objects even if they are only on the edge of visibility. The planets being labelled is usually the default, and you can take away the labels if I want to, for example if the names of Jupiter or Saturn’s moons are getting in the way. The next icon will bring up the labels for deep sky objects, happily labelling things completely invisible to the naked eye, this is usually off. All of those things are easy enough to use and quite useful, though some of the other icons on the bottom tray hardly ever get used by me, such as the equatorial versus azimuthal mount. If you are using a telescope and know what kind of mount it’s using, this can give you more accurate idea of what viewing the sky with it would be like. There’s also an icon for bringing any selected object into the middle of the screen, centering it, but you can do the same by hitting the spacebar, which is what I normally do. You use the left mouse button to select objects by clicking on them, and left clicking anywhere else will deselect that object.

Right clicking doesn’t really do much on its own, but it does participate in some of the combined or chorded hotkeys. Some functions in Stellarium are accessed by hitting many keys at the same time, such as scrolling through the years without using the time and date window. Most things are simpler and often there are multiple options to achieve the same result. For example, you can drag the sky around by holding the left mouse button and dragging the sky around by the selected point, or you can shift your view using the arrow keys. You can zoom with by holding the control key and using the arrows, which lets you zoom in or out as much or as little as you want, or you can use the forward slash or the back slash to jump close to or far away from the selected object with less fine control. If you are taking a closer look at something, having it selected and centered is important unless time is truly stopped. If time is really paused, you can deselect the object and it will stay there. If time isn’t paused then the Earth will continue turning and your view will be pointed away from the object, it will appear to move out of view.

Moving back to the side tray, when you bring up the location window, you of course have any location on Earth. There is also a drop down menu with all of the different planets, minor bodies, asteroids, moons, there’s loads of solar system locations that you can visit and check out the view from. The time and date selector is reasonably straightforward, but it does give the option of viewing the Julian time as well as the Gregorian time. Gregorian is the standard in most part of the worlds today, but the Julian system si still used in some parts of astronomy, such as epochs. You can type in whatever time you’d like, or you can scroll up and down through time. Moving onto the sky and viewing options sub-menu, there’s a lot we can do here, including the light pollution slider which is one of the most useful things for me. It also includes the meteor rate, which you can turn up incredibly high, it maxes out at 240,000 meteors and hour, the highest ever rate recorded in 1833, for an exceptional Leonid shower.

Moving through the sections of the sky and viewing options, there’s various other things you can do as well. There’s options to show the orbits of various planets and other objects in the solar system. There’s also access to the Solar System Editor if you have that plug in set to load when Stellarium starts up. This allows you to add in your own objects to the Solar System. For example if you wanted to see what it would look like if there was a planet like Saturn much closer to the Earth, you could drop that into the Solar System Editor and take a look at what that would look like. There are a number of plug ins you can select in the configuration window. There are also a number of different object catalogues. These are mostly deep sky objects, and many catalogues duplicate other catalogues, but with different designations for the same object to suit certain uses. You can filter objects by catalogue, but this isn’t a part of Stellarium that I use very often. The next section is, it’s where the sky markings are found, including the grids like the equatorial grid. This means that there a few things that you can select in menus, from the bottom tray, or by hotkey. This window is what I use to bring up the ecliptic, although it does have a hotkey as well. The sky and viewing options menu has a lot of subsections, including one for the various landscape options. I generally stick with the default, though I’ve used the Zero Horizon in videos before. The Ballycroy landscape is one I downloaded, it doesn’t come with Stellarium by default. It’s a location in Ireland, a Dark Sky park, coterminous with the Wild Nephin National Park. That landscape also labels various geographical features of the area. Next is the subsection on sky cultures, changing the names of stars or the constellations to represent other cultural traditions. The modern, mostly Greek and Roman constellations are far from the only ones, and there are a lot more sky cultures after getting added in with the newest update. Lastly, there are various surveys that you can pull objects from. Surveys are usually based on a particular telescope, often looking at a particular area, and collects all the objects it sees or discovers. There are a lot of list of objects that you can pull in to Stellarium if you’d like to take a look at something that doesn’t feature by default. The SIMBAD catalogue is the usual source and can be accessed from the search menu once you’re connected to the internet and pick a server to use.

Being able to turn down the amount of light pollution is one of my favourite features, it’s a great way to show people how beautiful the sky can look under the right circumstances, especially if they’ve never seen a truly dark sky before. Being able to turn the rate of meteors way up is nice as well, even if the maximum is an incredibly rare event that many people will never see in real life. One quirk of Stellarium is that meteors will only appear if time is moving at its normal rate. The amount of meteors visible during the incredibly high record Leonid rate is impressive enough that I have mentioned it in previous video and it’s always nice to find an excuse to show it, even if normal meteor showers pale in comparison. t

Moving down to the search window, this is another phenomenally useful feature of Stellarium. It’s especially useful for finding objects we can’t see with our naked eye such as Pluto. At the moment Pluto is above the horizon along from a little after sunset to just before Mercury rises, putting it in the sky with nearly every other planet.

Just by using control and the arrow keys to change how much of the sky is visible, shifting the direction of view by dragging the sky with my mouse, hitting L to speed time forward, K to stop it when I feel like it’s gone far enough, we can slide forward to the right time and get the right view to see that Pluto sets in the West before Mercury comes up in the East.

That’s a little unfortunate, we won’t have the dwarf planet in the sky with almost all of the major planets. In fairness, Pluto will be up with Mars, Jupiter, Uranus, Neptune and Saturn, we’re only missing Mercury and Venus. Looking at the next few days, Mercury will be coming up just before Saturn goes down, so they’re most of the planets will still be visible in the sky together. This will look especially fantastic in the countryside, even if there isn’t an exceptionally major meteor shower going on.

The configuration window is very useful as well. As I mentioned you can save your default settings in this menu. It also lets you choose the amount of information you want to show on any object you’ve selected. I always go with showing all possible information, but you can trim it down if you’d like. There are various extras available here and getting extra catalogues for stars is handy especially certain distant objects. The time settings here decide the time shown at startup, I just use the system time and date as I’m looking at the sky from where I am. Stellarium will normally adjust if you travel from your default location to somewhere else on the map, but if you physically move then your computers time will need to be updated. There are also options for a planetarium. Even though Stellarium is a free software, you can use it through various projectors to create a planetarium, as long as you have the curved surface to project onto.

There is also a professional version of this software. I use Stellarium almost exclusively, but there is a version called Nightshade, from a company called Digitalis, which was developed out of the same software as Stellarium. However, it is designed for major installations. It’s a much more powerful but much more complicated system designed for planetaria of various sorts, such as the ones in science museums and observatories. Follwoing this are various scripts, journeys that other people have created. You can use them, for example, to look at various solar eclipses that have happened, or be guided through the constellations of different cultures, there’s a few different things that they can show. Next are the plug-ins, of which I have a few active, such as the Solar System Editor. There are a lot of different things here, including remote control which let’s you control a telescope using Stellarium, really useful and powerful feature.

Way up in the top right corner are the icons for simulating the view through a telescope, binoculars or sensor. I have made a whole video on, but now the limiting magnitude is shown. This is a new feature, the limiting magnitude is roughly how faint of an object you could see using whatever tool you are looking through. With a reasonably big telescope we can see objects a faint as 15.72, for example. In the video I demonstrate this by looking at Betelgeuse, but of course we’d be able to see Betelgeuse. I almost tried to pick out something fainter, but I knew I would end up getting distracted looking for interesting objects in the sky. If that’s something you’d like to see, you can take look at any of my other videos.

I hope you enjoyed this quick run through the basics of how to use Stellarium. I use hotkeys for certain things, the arrow keys with control if I need to zoom in and out or just the arrow keys to move around, J K and L to orient yourself in time, and the = and the – to go forward or back day by day. In other cases I use the tray icons, in still others I dive into the menus and sub-menus. I will certainly go over the functioning of Stellarium in the future, but I hope that you enjoyed this piece. If you did please do like it, and if you’d like to support more pieces and videos then you can subscribe to this website and my YouTube channel. Hopefully, I’ll see you back here next time.