Atari Planetarium puts the galaxy on your monitor. You can recreate past celestial events, or plot future ones. Set it for any hour and date between 9999 B.C. and A.D. 9999, and the Planetarium will show where the heavenly bodies were or will be then. The program even accounts for the change from the Julian calendar to the Gregorian in 1582, when 10 days in October magically disappeared to accomodate the new way of reckoning.
The Planetarium plots the movement of these bodies with a time clock that can go backward or forward at up to 64 times faster than real time. If you move the cross-hair cursor off the screen, the picture scrolls in that direction. You can even make printouts, but unfortunately the cursor appears on them.
The Earth is "transparent," so that celestial objects are visible through the planet. For example, if the computer's vantage point is set at San Francisco in the late morning, you can still see the moon on the screen.
SKY is the normal display mode. MAP lets you select a location on Earth from which to view the heavens. SET selects the time and date. CHART, used chiefly for printouts, , allows you to view sections of the celestial sphere without obstruction by the horizon, and with north always directed upwards for easy orientation.
Planetarium is also full of interesting options. LINES draws line diagrams between stars to help define constellations. NAMES displays three letter abbreviations next to constellations. SYMBOLS marks planets with their respective astronomical symbols. DEEP SKY displays very distant galaxies. TRACK records the orbits of two celestial objects, such as a planet and a moon, to determine their closest approach. SOUND turns the cursor into a space shuttle, complete with noise.
The 115-page instruction booklet contains latitude and longitude tables for almost 200 locations on the Earth, lists of stars and constellations, a few future astronomical events and mathematical conversions. An example in the manual shows Halley's comet over Wollongong, New South Wales, Australia, on April 5, 1986.