Learning Stellarium: Those Wacky Wandering Planets
The purpose of this exercise is to learn the basics of Stellarium, to learn a little bit about planets, and to (hopefully) have a little fun. Stellarium is a FREE planetarium software for MacIntosh, Windows, or Linux computers.
Before trying anything else, let’s see what kind of help Stellarium has to offer. There is a control belt in the lower left hand corner of the screen.
This should put up a screen that has a “crib sheet” of keys that can be pressed to control the Stellarium program. This is a good thing to keep in mind.
The next thing to try is some of the controls. Since you are probably doing this during daylight hours, and you if you have your program properly configured, for your location, I’ll wager a guess that you see a lot of blue, and the sun. Let’s make it more interesting by “turning off the atmosphere.” The program simulates the scattering effect of the earth’s atmosphere. (Remember the real sky is blue due to scattered light!) With all the scattered light from the sun we can’t see stars during the daytime. We’ll turn off the atmosphere for a while. In the control belt (the belt thing to the lower left) there is a square that looks a little like a square yin-yang symbol. If you can’t find it, use your mouse to move the curser over each box until you find turn on/off atmosphere.
Use your arrow keys to navigate around the sky for a while. There are two modes of navigation. One is Alt-Azimuth the other is Equitorial. To switch between the two, you can use the button in the control bar, or just press the enter key. I would suggest starting off with the Alt-Azimuth setting until you are comfortable with that. Then try the equatorial setting.
As you are moving around, you probably see something interesting. Perhaps it is a planet, one of those things labeled with an “M” followed by a number, or perhaps little Pluto has caught your eye. Let’s go look at what you are interested in.
· If there are no objects labeled with an M then press the “n” key.
· Move the cursor over to the object
· Press the left mouse button. There should be a box cursor around the object. If not, try again.
· Once you have selected the object, press the space bar. The screen will move until the object is centered in the screen.
· Use your page up/down keys. Which one zooms in on the object?
o If you zoom in far enough a close up picture (usually from the Grasslands Observatory) will appear.
· Zoom in to look at the object, then zoom out and look at another object until this feel comfortable.
Now try playing with time. You can speed up time by pressing “l” and slow down time by pressing “j.”
· Press the “l” key about 4 times and watch as things start to really move.
· Look at the time reading in the upper left hand corner.
· Press the “j” key a number of times. Time should slow down.
· Keep pressing the “j” key until time reverses.
o You can tell when time has reversed by looking at the time in the upper left hand corner of the screen.
o You should also look at the directions stars are moving.
· Once you have gone through the time warp, press the “k” key to return the speed of time to normal.
· Press “8” to return to now.
One more way to adjust time is by pressing “=” and “-.” “=” will step forward by 24 hours. Pressing “-” will step back in time by 24 hours.
But what if we want to see what the sky will look like tomorrow night at 10:00 pm.? Well we could rush forward in time and then stop at the right time, or we can just set the time in the control panel. Try that.
· If the atmosphere is turned off then turn it on.
· Click on the control panel icon in the control belt. The control panel icon is the one that looks like a wrench.
· The control panel should open. Click on the tab in the control panel labeled “Date & Time.”
· Set the time for tomorrow at 10:00 pm. To do this, use the triangles to the left of the hours, minutes, and day. I wouldn’t worry about getting time to the last second.
· Close the control panel
· Turn the atmosphere back on and see if everything makes sense. (Should the sky be blue at 10:00 p.m.? Is it blue in real life at 10:00 p.m.?)
Finding a Named Object.
Let’s find a named object in the sky. Will Jupiter be in the sky tomorrow evening at 10:00 p.m.?
· Set the time to 10:00 p.m.
· Click on the “find object button.” This is the button in the control belt that looks like a magnifying glass. The “Find Object” box should come up.
· Type in “Jupiter” and click on “GO”. The sky should shift around until Jupiter is centered in the field of view.
· Close the “Find Object” box as soon as you find the object. I have a tendency to press return and jump off to another object.
· Will Jupiter be up tomorrow night at 10:00 p.m.?
The word “planet” comes from the Greek “πλανήτης” which mean “wanderer.” What were the Greeks talking about? It is time to do some virtual observing.
· Start by switching to equatorial mount. (This assignment can be done in Alt-azimuth mode, but things rotate funny.) The Equotorial/Altazimuth button will turn white, as shown above, when in Alt-alzimuth mode.
· Set the time to May 02, 2007 at 10:00 pm (22:00).
· Find Antares using the locate object command.
You should see something similar to the picture on the last page of this handout. The difference is that the date will be different, the planet Jupiter will be near by, as will the dwarf planet Pluto.
· Mark the location of Jupiter on the paper map.
· Now step up forward one day at a time and watch what happens to Jupiter.
· Keep stepping forward until September 19, 2007
· Mark on your paper the path Jupiter takes, relative to the background stars, such as Antares.
For extra credit, when would be a good time to look for Mars’s motion? With Mars, it is easier to show what it called “retrograde motion.” Look up this term, and find a time frame that shows this motion. A correct answer should give a reference star, such as Antares, the time to start watching, when “retrograde motion” begins, when “retrograde motion” ends, and when to stop watching. A good way to do this is to turn off the ground, turn off the atmosphere, speed up time and watch Mars.
The real extra credit assignment is to look at the night sky. Now that you know when Mars (or another planet) will go through retrograde motion you could go out and really watch it happen. A digital camera (even a cheap one), a computer and the patience to take pictures of the night sky for a month should be all you need, thought I must admit that I haven’t tried this out… Yet!
Note that I have reversed the colors in this picture to save on printer cartridges. That is why black is white, white is black, and grey is grey.