Figure 10 is a screen grab from the running applet. To try this virtual experiment, select the ATLAS icon to start the applet.

See the list of other virtual experiments.

VIRTUAL EXPERIMENT 2
Parallax Effects on a Starship Ride

• Understand the effects of perspective foreshortening.
• Visualise parallax effects due to the observer moving a great distance in a straight line.

• Set the operation mode to perspective projection.
• Set the field of view to 45 degrees.
• Slowly change the field of view, making it smaller and smaller.

• Beginning with a large field of view, stars appear to shift position when the field of view is set to smaller and smaller values.
• Stars close to the viewpoint appear to shift more than stars further away.
• This is similar to watching street lamps on a long, straight road. Lamps close to the car appear to move quickly. Lamps further away appear to move more slowly.
• The applet changes the viewpoint in deep space to the distance required to fit the entire solar neighbourhood into the specified field of view. A large field of view places the viewpoint closer to the solar neighbourhood than a small field of view.
• The apparent magnitude of each star changes as the viewer gets further away from the sun.
• When the field of view is small enough, stars no longer appear to shift position. At this point, the viewer is far enough away to reduce the effects of the perspective projection, such that we are essentially left with parallel projection as in virtual experiment 1.