Stargazing sessions with Stellarium
Posted by Greten on 03 May 2013 under Free Instructional Applications
One of the most interesting activities in science classes is conducting stargazing sessions using a telescope. The school might have its own telescope, the science teacher may arrange for an educational field trip to an observatory, or the students may bring if they own one and it's convenient to carry. However, to have a worthwhile stargazing session, you need to prepare for it by determining the exact date, time and place, and what would be the position of celestial bodies on that date and time as seen from that place.
Digital starmaps are among the most useful products of the digital age. Before digital starmaps where made, people have to rely on thick tomes of catalog to forecast which heavenly bodies will appear in the sky and plan their stargazing session accordingly. A basic digital starmap will have the options for you to input the time (date and exact hour and minute) and location (in terms of latitude and longitude) and it will show you how the celestial bodies will be positioned in the sky as seen from that particular location.
The earliest digital starmap that I was able to use is the Skyglobe by KlassM Software Inc., a DOS-based and non-opensource freeware (i.e., it is free but its source code is not available). I also made my own digital starmap with capability to predict eclipses as an undergraduate thesis.
Now that we cover digital starmaps in general, let's proceed to Stellarium, one of the free and open source software (FOSS) digital starmaps. There are others but I haven't taken a look at them yet. Similar to Skyglobe, Stellarium shows planets, stars, constellations, and nebulae as seen from the specified location at a specific time. Stellarium was developed by Fabien Chereau in 2001 and was released under GNU General Public License and available in GNU/Linux, Mac, and Windows.
I will discuss few of the functions that you might use often. It's actually quite easy to navigate on the menus and options so you can just explore it yourself.
For Ubuntu, Stellarium is available through Ubuntu Software Center. You can search it there and when it appears, click the Install button.
For Windows, the installer is available on sourceforge. Just download it, double-click the downloaded the EXE file and follow the instructions that appear.
I'm not sure about Mac as well as the non-Ubuntu Linux forks as I never owned any of them. You can find the installers for different OS that are supported here, as well as instructions on how to install them.
Depending on your operating system (OS), the Stellarium icon should appear on your Desktop or 'Programs' panel or both. In Ubuntu, it appears by default under the Science folder in the Main Menu.
Projections of the sky
If you drag your mouse on the main screen (the part where you see the stars, planets, etc.), you will get different possible projections. I will not tell you how to drag the screen to get the different projections, you will be able to figure it by yourself if you already opened Stellarium and experiment a little bit. The changes between the projections is fluid but for the sake of this discussion, allow me to compartmentalize the possible projections into three.
This is probably the most realistic as you can see the "horizon", the point where the sky meets the ground. You need to drag it left or right to see the different celestial bodies that are visible on the specified time, and this is analogue to rotating your head or entire body while standing on a plain ground. This is ideal if you are bringing a laptop on the location of your stargazing and want to see a close approximation of what you would actually see.
sky dome projection
In this projection, the whole sky is compressed within a circular area with the ground surrounding the sky like some sort of ring. In this projection, you will see all the visible celestial bodies as seen from the specified area on a specified moment of time. You see it as if the sky is a dome and you are looking-up to it. This is ideal for printing the sky map on a paper.
When I said "all the visible celestial bodies", they do not include those that were intentionally made to be invisible using the Sky and viewing options (can be opened by pressing F4) as well as those that are not yet included in the database of Stellarium.
Here, the ground is compressed into something like a small ball or planet with only those celestial bodies near the horizon being visible. You can also think of it as having the sky as a dome, except that you are floating on top of that dome looking below. I could not think of any practical use of this projection. Maybe it's just there as a consequence of the projections of Stellarium being continuous.
I just made-up the names of these projections and you need not to memorize them, you only need to understand the description I provided.
Some useful shortcut keys
Except for the last two, the functions of these shortcut keys can also be accomplished by hovering your mouse on the lower-half of the screen on the left side. A panel with icons will appear there. Clicking on these icons have the same effect as F1 to F6.
- F6 - location: set the latitude and longitude or search for your city from the list.
- F5 - date and time
- F4 - sky and view options window: several things you can do here such as:
- setting a class of celestial bodies visible or invisible
- setting the ground (ocean, trees, grass field / Guereins, etc)
- enable or disable atmosphere
- F3 or CTRL + F - search celestial body
- The starmap will reposition itself and put a marker on the celestial body being searched.
- If the starmap repositions itself but you cannot find the marker, make the ground invisible by pressing G or clicking the "Ground" button at the bottom panel. You should be able to find the celestial body with the marker. It's not yet on the sky. Press G or click the Ground button again to make the ground reappear.
- F2 - configuration
- F1 - help
- CTRL+S - save the screenshot as stellarium-nnn.png in the Screenshot Directory, where n is an integer from 0 to 9. By default, the Screenshot Directory is the Home folder but you can modify this by pressing F2 to open the Configuration window and going to Tools tab.
- Print Screen (PrtSc) - save the screenshot as image file in Ubuntu, or copy to clipboard in Windows
- CTRL+Q - close or quit Stellarium.
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