This Java application computes sunrise and sunset times for any desired location on Earth. You may simply click a map for US "lower-48" locations, or select from drop-down lists of US and world cities and airports, or you may type in a custom position.

Click here to open the sun computer

From the perspective of an observer on the Earth, the sun makes some obvious, and also some subtle, motions across the sky.

The first and most obvious is the daily rotation around the sky, east to west, with a duration of 24 hours. The second is a seasonal north-south motion of ± 23° 27' away from the equator.

The third motion is a subtle change in the sun's noontime position, brought on by the earth's non-circular (elliptical) orbit around the sun. Because of these two seasonal motions, if a camera were to be set up and the shutter opened for a moment each noontime, over a year the film would record the image in Figure 1.

A program that keeps track of the sun (called a solar ephemeris) must accurately represent all these motions. If it is to calculate sunrise and sunset times, it must also accept earthly position entries as well.

Sun Computer first calculates the sun's position very accurately, then it applies this information to the problem of computing sunrise and sunset times.

Click here for a Sun Computer tutorial.

If you cannot see the Java applets on this page, you need to enable Java in your browser. Here is how:

• Netscape:
  Select Options > Network Preferences > Languages > Enable Java

• MSIE (<5.0+):
  Select View > Options > Security > Enable Java Programs
  
  
• MSIE (5.0):
  Should be on automatically

The Java application and the above information is © Copyright 1996,
P. Lutus, www.arachnoid.com