ASA Certification Standards: ASA 107, Celestial Navigation

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Prerequisites: None but basic sailing and coastal navigation experience recommended.

General Description: A certified student is able to demonstrate the celestial navigation theory required to safely navigate on an offshore passage.

I. Sailing Knowledge

• Convert longitude into time, calculate the zone time given longitude.
• Convert standard time and zone time to G.M.T.and vice versa.
• Calculate the chronometer/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 Polar Star.
• Solve the navigational triangle using HO249 tables and explain all calculations.
• Plot celestial LOP on a Mercator projection or on a universal plotting sheet.
• Calculate the times (ship’s and G.M.T.) of sunrise, sunset, and twilight.
• Determine the approximate azimuths and altitudes of the navigational stars and planets at twilight, using a Star Finder.
• Calculate and plot the lines of position obtained from observations of several celestial bodies at twilight and thus find the boat’s position.
• 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.
• Calculate the true bearing of a low altitude celestial body in order to determine the deviation of the compass.

II. Sailing Skills

Blue Water Sailing School provides offshore passages for practical application of the Celestial Navigation standard.

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