If you have used astronomy related free software and would like to have it added to the information below please add your comments below to share your experience.
The following software programs are available on the web and are free. They are quite different in both how they work and the information that they represent in the night sky. Each has different advantages and disadvantages but can help anyone with learning the about what is up there and where it is.
As with any software for working with the sky, after downloading and installing it it is important to define your initial use parameters such as location and timezone. Until that is done, the information presented will not be very useful.
Halo Northern Sky presents entire the sky similar to the way star charts do. After setting the initial parameters it is relative simple to use. For most people, especially novices or those with limited computer resources, the Small Basic Package should be adequate. It is available at Halo Northern Sky Web Site.
Some of the many possible display formats are available as screen shots at Halo Northern Sky Screen Shots.
Stellarium (for Windows, Linux, Mac OS) presents the sky in a more realistic way, trying to make it appear as it does when you are outside looking up. It is a bit more complicated to use than Halo Northern Sky but has the advantage of displaying the sky in a way that is more like it naturally appears.
Most users will find the Default Catalog of Stars of over 600,000 objects to be adequate. Loading the additional available catalogs could significantly slow the program’s start-up on slower or more resource taxed computers.
While it is not free but is relatively inexpensive, if you have an iPhone, iPad Touch or iPad, the App Store has Star Walk that has proven a wonderful tool for learning and use during observing the night sky.