This program is shareware. If you find Navigator Light useful and want to download the latest version, with many extra features, get free support via email and collaborate in improving its capabilities, you can register for only US$35.
Click here to read more about the registered version.
The figure below shows the list of visible stars (those with positive altitudes) in a given time and position. You can click a star on the polar chart and see it's data (Name, Altitude and Azimuth). Or you can point on the spreadsheet and see the corresponding star on the chart.
In this chart, the celestial objects are
represented by the bitmaps on the left. The center of the chart
is the Zenith and the external circle is the horizon. The two
blue circles are the 30░ and 60░ altitudes. The best stars to
observe are between these two circles.
Calculating a Line of Position is easy. Input:
Press Calculate. The LOP will show in the chart, as illustrated.
All input fields and buttons have hints that explain what they are and what units should be used. Place the cursor over the field to see the hint.
After you calculate two or more Lines of Position, you can calculate your astronomical position. The figure bellow shows an astronomical position calculated with 3 LOPs. Note the blue chart, showing the LOPs. The astronomical position is indicated by the white circle. Use the cursor to zoom in and out. Double click a LOP in the spreadsheet to edit or transport LOP.
The altitude of the same celestial object in two different times may be used to find the position. For example, you can draw two Lines of Position for the Sun, one in the morning and one in the afternoon. If your boat is moving, you will have to transport the first line to the second position.
Navigator Light allows the transport of LOPs. In the page "Astronomical Position", double click a LOP. The following dialog will show:
If your boat travelled at 5 knots for 3 hours in direction 235, move the first line 15 NM in direction 235. Just enter the data and press the Transport button. Then recalculate the astronomical position.
Navigator Light - particularly the visible stars command - does a great deal of floating point calculations. The use of a computer with numeric coprocessor is recommended. This particular command, that takes less than 0.5 sec on a Pentium 133, takes 12 seconds in a 486 SX 25.
Some people don't like the idea of taking a computer to the boat. Computers are generally not rugged enough for boat conditions. They may consider downloading the previous version of Navigator Light - developed for DOS - that works with HP 95 LX palmtops. This is a small computer that runs on AA duracells. And will work for a couple months with the same batteries (minimal use). This version is available on demand.
For the technically inclined.
Celestial navigation fundamentals | On Line Almanac