Celestial Navigation Pac contains several menu-driven
applications that allow you to:
- Compute position fix from two or more celestial
- Plot lines (circles) of position.
- Estimate position from single observation combined with dead
- Compute running fix, accounting for the motion of the
- Compute course and distance for rhumb lines and greater
- Refer to a built-in accurate and complete astronomical
An extensive Navigation Tutorial in the manual leads you
step by step through a voyage from San Diego, CA to Honolulu, HI. A detailed example
introduces issues such as dead reckoning position at the beginning of a voyage, route
planning , inputting celestial observations, entering sun sights, position fix, running
fix, evening star sights, moon/planet fix, and dead reckoning as third observation.
Corrections for sextant observations use atmospheric pressure and temperature. Route
planning helps compute the course via rhumb line and great circle routes. One can take
advantage of evening star sights from the built-in Almanac program.
A short and a long list of stars, as well as a list of
Greek letters and a list of constellations are included in the application. The stars are
represented by their "Bayer designation".
In a special directory all the navigation data is saved
under simple variable names specified by the user. The data editor in saves observations
in a user-friendly file for later access.
The Running Fix
Is computed from observations widely separated time,
obtained when the vessel is moving. Two built-in programs, (ADDOB and ADV), tackle the
task of computation using different methods. By selecting a time when the fix is valid,
the ADDOB program will automatically advance or retard all observations to this time,
yielding a running fix. The ADV program advances the observations by correcting the
Greenwich Hour Angle and the declination of the observed body. This correction depends
somewhat on the position, and hence current dead reckoning position is used.
Two kinds of errors commonly encountered in navigation are
analyzed in this Pac: random and systematic. To minimize random errors, the user is
encouraged to take a number of observations so that a least square fit analysis can be
used to compute random errors. Systematic errors are minimized prior to the start of any
voyage by taking observations from a known location and comparing the celestial result
with your own true position. If there are no systematic errors, the uncertainty in
location of the position is 0.25 nautical miles.
The SAIL program computes the course and distance of a
voyage using the rhumb line, great circle or composite route. A great circle route does
not follow a constant course; the courses are "true" and not "magnetic".
A great circle route can be planned in a series of short rhumb lines, by setting up a
series of waypoints. The program can compute the vertex of the great circle. Composite
route planning allows a combination of great circle planning and placing limitation on
latitude beyond which the user does not wish to sail.
The Pilot program allows dead reckoning, distance off by
vertical angle, distance off by two bearings, current set for drift, tide interpolation,
true course versus magnetic course, and a distance/speed/time calculator.
Eighty-nine stars are listed in the pac, using their Greek
The Celestial Navigation Pac comes with a very handy manual
that includes a quick reference section for sight reduction and running fix, a quick
reference guide for the menu structure used in the pac, an extensive glossary, and a set
of frequently asked questions. The Celestial Navigation Pac was developed by an expert
sailor while working at the University of Hawaii.