From Ink to Electrons

When we redesigned our Web site in 2002, we looked for ways to use the site to complement what we print in the magazine. For the reasons just outlined, it seemed obvious that we should create an electronic sky chart modeled on the ones in Sky & Telescope but customizable for any location on Earth, on any date, at any time. So that's what we did!

Sky & Telescope's Interactive Sky Chart is a Java applet based on the same data and algorithms we use to plot our monthly evening sky charts. Its principal creators include senior editor Roger W. Sinnott and associate art director Steven Simpson, the brains behind our printed charts, as well as engineers and programmers at the Interactive Factory in Boston.

In case you're unfamiliar with Java applets, these are self-contained applications written in the Java programming language pioneered by Sun Microsystems (S&T: June 2001, page 58). When you use a Java-enabled browser to view a Web page that contains an applet, the applet's code is transferred to your computer and executed by the browser's Java Virtual Machine. Java applets are supposed to work on all computers and operating systems, but because the major players in the computer industry haven't yet agreed on uniform standards for the language, this "platform independence" hasn't been fully realized. To find out whether our sky-chart applet will work on your computer, review our system requirements.

Although we developed our interactive sky chart mainly to provide newcomers to astronomy with S&T-style constellation maps for their particular location and observing time, we soon discovered that the applet has many other uses. Some should appeal to more advanced amateurs and, especially, to teachers and students at all grade levels. By changing the observing location, date, and time in certain ways, you can use the applet to gain a new appreciation of the mechanics of the solar system and the sky's daily, monthly, seasonal, and annual cycles. You can also use it to do a bit of astronomical detective work. Let me walk you through some examples to show what I mean.