Which version should I use?
Stellarium Web — start here
Runs in your browser, including on a Chromebook. Nothing to install and nothing to ask permission for. It does everything this class needs.
Needs an internet connection.
Desktop app — optional, for home
Free for Windows, Mac, and Linux. More features, keyboard shortcuts, and it works offline. Worth it if you have your own computer and get hooked.
There are phone apps too, but some features cost money. You don't need them.
Set it up
Do these three things every time you open Stellarium. Pick your version and the directions will switch to match.
Set your location
Click the location name in the bottom-left corner. Allow location access, or search for your town, then close the panel.
The sky looks different from different places on Earth. If this is wrong, nothing else will match.
Set the date and time
Click the date and time at the bottom right. Change the time with the arrows or slider — try 9:00 PM tonight.
Stellarium starts at right now, which is often daytime. Set it to when you'll actually be outside.
Turn on the layers you need
Use the buttons along the bottom bar: turn on constellation lines, and turn off the atmosphere if the sky looks washed out. Hover over a button to see what it does.
A bare sky full of dots is hard to read. Lines and labels turn it into the patterns on your star map.
Controls you'll use · Stellarium Web
| Look around | Click and drag the sky |
| Zoom in and out | Scroll wheel, or pinch on a touchscreen |
| Get info on a star | Click it |
| Find something by name | Search box at the top |
| Constellation lines and names | Buttons on the bottom bar |
| Remove the daytime sky | Atmosphere button on the bottom bar |
| See through the ground | Landscape button on the bottom bar |
| Back to right now | Date/time panel at the bottom right |
Reading the info panel
Click any star and a panel of numbers appears. These are the four that matter for this class.
- Magnitude
- How bright it looks. Smaller numbers are brighter; Sirius is about −1.5, and the faintest stars you'll see from a backyard are around 4.
- Az/Alt
- Where it is in your sky right now: azimuth (compass direction) and altitude (height). These go straight into your Observation Log.
- RA/Dec
- Its address on the celestial sphere. It barely changes, which is why star charts can use it.
- Rise, transit, set
- When it comes up, when it's highest (crossing your meridian), and when it goes down. Transit is the best time to look.
Your first observation
This is the routine for every entry in your sky journal: plan it in Stellarium, go look, then write down what matched and what didn't.
- Set tonight at 9 PM
Location and time first. Look at the horizon letters to find which way is south.
- Find this season's anchor
Check the "find tonight" list on your star map's seasonal chart and locate that pattern in Stellarium.
- Click the brightest star in it
The info panel shows its name, brightness, and where it sits in your sky.
- Read altitude and azimuth
Az/Alt is the line you want. Azimuth is the compass direction; altitude is how high above the horizon.
- Convert to fists
Divide the altitude by 10. That's how many fists up you'll measure outside.
- Go out and check it
Find the same star in the real sky, fill in your Observation Log, and use section 5 for anything that didn't match.
If something looks wrong
You'll use these with it
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