ASA Celestial Navigation
General Description: Able to demonstrate the
Celestial Navigation theory required to safely
navigate a sailboat on an offshore passage. The
practical application is conducted in the Offshore
A Certified Sailor has successfully
demonstrated his or her ability to:
- Convert longitude into time.
- Convert standard time and zone time to GMT
and vice versa.
- Calculate the zone time given longitude.
- Calculate the chronometer (or watch) error
given a previous error and the daily rate.
- Apply the corrections for index error, dip
of the horizon, and total correction to convert
sextant altitudes of the sun, stars, planets,
and moon to true altitudes.
- Calculate the time of meridian passage of
the sun and calculate the boat's latitude from
the observed meridian altitude of the sun.
- Determine the latitude at twilight by means
of the Pole Star.
- Solve the navigational triangle using a
navigation table and show all appropriate work.,
- Plot celestial lines of position on a
Mercator projection or on a universal plotting
- Calculate the times (ship's and GMT) of
sunrise, sunset and twilight.
- Determine the approximate azimuths and
altitudes of the navigational stars and planets
- Calculate and plot the lines of position
obtained from observations of several celestial
bodies at twilight and thus find the boat's
- Advance the LOP obtained from a sun sight to
another LOP obtained from the sun at a later
time and find the boat's position using a
running fix (sun-run-sun).
- Calculate the true bearing of a low altitude
celestial body in order to determine the error
and deviation of the compass.