What's that bright thing over the wood shed? Is it a UFO or Venus? Grab your Palm Pilot and find out!

Planisphere is an interactive program modeled on the astronomical device of the same name. It displays the sky as it appears right now at your location - or at any other time and place you select. With a clean, uncluttered design, it is ideal for quickly locating stars, constellations and planets in the night sky.

Using Planisphere requires no prior knowledge of astronomy. All you need is a little curiosity, good eyesight and a clear night sky. If you're interested in stargazing, Planisphere is a great learning tool to help you get started.


What Is A Planisphere?

pla-ni-sphere, n. [plane + sphere]: a projection of the celestial sphere onto a planar chart showing the stars visible at a particular time and place.

A planisphere consists of two wheels. The bottom wheel is a star map, and the top wheel has an oval cutout - the horizon. As the star wheel turns, different parts of the map become visible through the oval, representing the stars rising above the horizon.


How Do I Read A Planisphere?

A planisphere shows the sky as you would see it lying on your back, looking up. If your feet are pointing south, then south is down, north is up, east is left and west is right. Note that compared to a regular map, east and west are reversed; this is because a regular map is a view from above, while a planisphere is a view from below.

Hold the chart up toward the sky, facing the direction that is at the bottom of the chart. The bottom half of the oval is the sky in front of you, the top half is the sky behind you.