This study unit will help you explore the appearance of the Moon, planets, bright stars and constellations in the night sky from a chosen point on the Earth at any time. It uses software enabling a virtual planetarium on the desktop.
Software and Websites
Stellarium is available for download for Windows, Mac OSX, and Linux operating systems by clicking on this link:
http://www.stellarium.org/ Stellarium - A free planetarium for your computer
We have installed it on the lab computers. If you prefer to use your laptop, or follow up later at home, the installation is fast and simple. Follow the instructions that are provided on the site. This is beautiful "award winning" software useful throughout the semester, and worth the effort to have available if it will run on your own computer.
Other web sites that are useful for this activity are
http://www.heavens-above.com/ Heaven's Above - The sky tonight on the web
http://www.iau.org/public_press/themes/constellations/ Constellations - Maps of the constellations
http://www.google.com/sky/Google Sky - An interactive map of the sky, the Moon, and Mars
First, there are a few things you need to know about using Stellarium. You might look at the Stellarium Tour on their website for an overview and reference to these options:
Stellarium starts in full screen mode and will cover everything. You can change this by pressing the F11 key to fit it into a smaller window.
There are two bars of menus, one at the bottom of the screen, and one on the left. They are hidden until you run the mouse down to the bottom or over to the left.
When you or done, you can use the bottom menu bar to exit by selecting the off button.
Setting your location
By default you will be in Paris, France. If you press F6 the location menu will pop up and you can select your city or put in longitude and latitude. Once you have done this and saved the configuration, Stellarium will come up at your chosen site. The location menu is also in the left menubar under the compass icon at the top left. When you have selected your location the menu will show a map of Earth with an arrow pointing to your site.
Setting the time
Stellarium starts with the sky over your site at this very moment. The date and time will show at the lower right, based on the computer's clock. This time is the local time at your computer. If you change your location, the time shown will still be the time at your computer, not the time at the new site. For example, if you are in Baltimore, Maryland and you set up Stellarium for that site, then the computer is in the Eastern U.S. time zone. When you run Stellarium at 3 PM it will show the afternoon daytime sky with the Sun. Should you use the location menu to change to Rome, Italy, the sky will go dark because it's nighttime there. The clock will still show 3 PM because that's the time where you are. You can change the date and time in two ways. One is with the time menu selected from the left menu bar Clock icon. The other is with the two arrow icons at the right of the bottom menu bar. These speed forward-reverse, real time rate, and now buttons let you speed up the daily motions of the sky, and then slow them down again when you have the events in view you want to see.
Change the direction you are looking by holding down the left mouse button and dragging your direction of view, or by using the updown leftright arrow keys on the keyboard.
Identifying planets, stars, and constellations
The lower menu offers options to add labels. By default the planets will be named, and you can turn this off using the Planets labels icon that looks like Saturn. You can outline the bright stars of the constellations, add constellation names, and even overlay mythological figures to help you see the patterns by clicking on the various buttons in this menu. There are two celestial grids offered too that show the equatorial celestial coordinates of stars (right ascension and declination), and the local sky coordinates (altitude and azimuth). A menu on the left for
Sky and viewing options
allows you to change the constellations, names and associated cultural folklore. Click that option, select
Starlore and Western
to see the the typical sky labels of American and European culture, or change to one of the others offered to see the diversity of named patterns in the sky. The same menu under
lets you select whether you would also like to see the constellation boundaries as red dotted lines. Sometimes it's helpful to see these in order to identify the constellation in which a particular object is located.
Identifying an object
Move the mouse over the object and click with the left button to have its identification displayed. Click with the right button to make this go away. Click with the center button (press down on the mouse wheel) to have the display center on this object after you have selected it.
Zooming in and out
The Page Up and Page Down keys on the keyboard zoom in and out of the sky. You can move around the zoomed in sky with the arrow keys or dragging with the left mouse button. The status display at the bottom of the view tells you the field of view
in degrees among other things. For some objects there is a photo that appears when the sky view is zoomed in close. When an object is selected and centered in the view, after zooming in the view will stay centered on it even as the day progresses. Think of it as a telescope that is pointing at your target, and tracking the target as the Earth rotates.
The Moon and planets will be labeled by default. You can turn these names off with the P or by clicking on the Planet icon on the lower menu bar. If you select a planet with a left mouse click, the sky view will lockto that planet and you can follow it during the night. Planets with satellites like Jupiter will show the satellites as they really would appear in a telescope, and in motion in their orbits around the planet.
You can find a planet or other objects by using the
The left menu has a Magnifying glass icon that brings up this option. So does F3.
Let's begin by watching the Moon to discover its daily, monthly, and annual cycles. Set your location in the software, and check that sunset occurs at about the right time.
Start on the first day of this month and advance the date one day at a time.
1. When does full Moon occur in late August 2012? Advance the day again, and find the next full Moon, and perhaps the one after that ...
2. How many days pass from one full Moon to another?
Notice the appearance of the Moon changes in the sky during the Moon, and that it rises at different times night after night.
3. From one night to the next, how many minutes later does the Moon rise?
As days pass, the Moon changes its phase, first from a thin crescent, then to first quarter, full, last quarter and new.
4. On what day and time in September 2012 does the last quarter moon rise?
If you have time and want to look into this further, notice how the point on the horizon where the Moon rises changes during the month, and from month-to-month through the year.