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Celestial Navigation (ASA 107)

Prerequisite: 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.

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 usinga running fix
  • Calculate the true bearing of a low altitude celestial body in order to determine the deviation of the compass.

Sailing Skills

Offshore passages for practical application of the Celestial Navigation standard.

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