Digital Universe Guide - Hayden Planetarium

28 3. THE MILKY WAY ATLAS
When you start the Milky Way Atlas, you are on a unique point. In Partiview it is called the Point of
Interest. The Point of Interest is the point about which rotations and orbiting take place. In the Milky Way
Atlas, it is set to the Sun’s location at (x, y, z) = (0, 0, 0). (You are actually positioned a negligible
distance from the Point of Interest for reasons we’ll discuss later in this section.)
Panning Around the Sky With the left mouse button pressed, move the mouse inside the
Graphics Window to pan around the sky. You will notice the stars, a few star labels, and the band of the
Milky Way. The stars resemble those in the sky in luminosity and color. We place a texture, or image, on
each, giving depth to the star field. If you don’t care for these textures, you can click the Polygon Toggle
Button to turn off the star’s polygons (the textures are drawn on polygons). Remember, for this change
to take effect, stars must be the active group. (A group becomes active when you right-click on its
Group Button or select it from the Group Menu.) Of course, once you turn the textures off, the stars will
all look similar to one another, so we prefer to have the polygons on.
Moving Off the Point of Interest Let’s exercise our navigational skills. Partiview starts in the Orbit
Flight Mode. You can confirm this by looking at the active flight mode printed below the Flight Mode
Menu, which should read [o]rbit.
You’ve seen what the left button does from this position; it moves your head without moving your
position in space. If you try holding the right button down, you won’t see too much happen. Because
Orbit Mode is a logarithmic flight mode, you will have zero speed when sitting on the Point of Interest.
Because you’re not exactly on the Point of Interest, you are likely to begin moving backward or forward
after some time, but who wants to wait?
Now, using the Flight Mode Menu, switch the flight mode to [f]ly. With the right button, fly
backward away from the Sun. Fly is a linear flight mode, so it remains the same speed no matter where
you are in the Atlas. Using the left button in Fly Mode, pan around a bit, keeping the Sun in view. Here
you’re moving your head but not your position.
Using the Keyboard to Switch Flight Modes Now switch back to Orbit Flight Mode. With the left
button, you will now orbit the Point of Interest, in this case the Sun. The bracketed first letter in each
flight mode may be used in the Graphics Window to switch flight modes.
To test this, activate the Rotate Flight Mode by pressing r (must be lowercase) in the Graphics