The Sky above Big Bear

This is an astronomical Java applet (or astronomical clock). If your computer is set to your correct time (and time zone), the applet will show you the correct Universal Time, our local time (in Big Bear, California), our sidereal time (star time), and a sky map that is updated every 20 seconds. During daytime the Sun will show up and the sky will turn bright. Sometimes you can still see the Moon and the planets, but they are best viewed at night. The Sun, Moon and the planets are all shown bigger than they would appear in the real sky, thus they should be easy to see. Sometimes, when the Sun and the Moon are very close together, the oversize will lead to false overlapping between the two.

The text gives some information that you can not see in the sky map. The solar and lunar altitude and azimuth tells you were the Sun and Moon are even when they are below the horizon. A negative altitude means below the horizon. The azimuth is the position angle of the object. North is 0, East 90, South 180 and West 270 degrees. The characters M,V,M,J,S,U,N represent the planets (Mercury, Venus, Mars, Jupiter, Saturn, Uranus and Neptune) and they light up whenever a planet is above the horizon. When a planet sets the light goes off. The lunar phase is given in fractions of the disk that is illuminated. A phase of 0.0 is thus new Moon (dark), 0.5 is half Moon, and 1.0 is full Moon (bright).

The coordinates of the Moon have a periodic error of up to +/- 10 minutes of arc (or +/- one third of the lunar disk). This is because the calculation of the lunar orbit is simplified to speed up the applet. This of course also means that the applet is unable to show solar and lunar eclipses.

If you want to know what an object is, you can press the LABELS button. If you want the stars to go away so that you can see the planets better, click STARS ON/OFF. If you want to see the sky some time later or earlier than the current time, set a time offset and wait for the next update (max 20 s). If you want to change to a different month or year, you can always change the time on your computer.

The applet is configurable for any geographical location, but only on the web server (when you put it into a new web page). Click here to see a version running in Sweden. If you are interested in a copy of the program for your own web page, please contact me.

Big Bear, California, USA, 12/11/97

(c) Anders Johannesson

The applet uses Java 1.1 and requires Netscape 4.03 or later, or Internet Explorer 4.0 or later with Java enabled.