One of the most interesting features in Planetarium is its use of time. You can use the Palm computer's hardware buttons to advance forward one step at a time. Hofer has carefully chosen his time intervals so that you can, for example, follow the annual path of a planet among the stars, including retrograde motion and conjunctions. It's even possible to get a rough idea of the circumstances of solar eclipses. Planetarium has a fee of $16.

Palm Globe
This application is actually the exact opposite of a star chart program, but it seems to fit under this heading nevertheless. Instead of showing you the sky as seen from Earth, Palm Globe shows you the Earth as seen from space. A sample graphic can be seen in Figure H. Author Mike Cowlishaw has included a number of controls to let you view our globe from different angles, and under different types of lighting. If you don't understand why the sun is up for 24 hours a day at the North Pole in the summer, this program may give you some help. Palm Globe is freeware.

FIGURE H

Palm Globe draws the Earth as seen from space in a variety of formats.