If you have visited a planetarium, you must know the experience of sky-watching. But in this age of technology, you need not go in search of a planetarium just to view the sky. Here I present you a very good planetariums on your computer.
Stellarium is a free GPL software which renders realistic skies in real time with openGL. It is a free open source planetarium for your computer. It shows a realistic sky in 3D, just like what you see with your naked eye, binocular or telescope. It has a default catalogue of over 600,000 stars. The multilingual and graphical interface has a powerful zoom, time control and fish eye and spherical mirror projection. If you are a science teacher, the eclipse simulation feature should be very helpful. Moreover, you can customize the location and time.
You can download Stellarium here.