Ocean Navigation Introduction

Corrections to Sextant, Time, Sunrise, Sunset, Twilight, Moonrise, Moonset, Finding GHA and Declination, Assumed Position and Local Hour Angle, Computed Altitude and Azimuth, Amplitudes, Interpolation, Altitude Intercept, Using Position Plotting Sheets, Plotting Lines of Position (Sun, Moon, Stars) LAN, Running Fixes.

This was designed to help you prepare yourself to pass the Coast Guard exam on celestial navigation oceans, or if you are just interested in learning celestial navigation. I have written this with three ideas in mind.

1. Make it as short as possible.
2. Make it in plain arithmetic and keep it in a form that is easy.
3. Use only the materials that will be available in the exam room.

You do not need a sextant to work these problems or the ones on the exam. Learning to use the sextant is a personal skill that is acquired by practice. The Coast Guard test has 10 multiple choice questions with a passing score of 90%.

The Coast Guard exam questions may cover:
1. Sight Reduction (Sun, Star, Moon)
2. Star Fixes
3. Running Fixes
4. Latitude by Meridian Altitude
5. Latitude by Polaris
6. Time of Local Apparent Noon
7. Time of (Sunrise, Sunset, Twilight, Moonrise and Moonset)
8. Deviation or Gyro Error by Azimuth
9. Deviation or Gyro Error by Amplitude
10. Identification of Unknown Stars and Planets
11. How to Select Stars for a Fix
12. Correction of Sextant Altitude
13. ETA Problems
14. Time Tick Problems

I will give you step by step instructions for doing all these problems. You will need PUB 229 (15-30) and a reprint of the 1981 Nautical Almanac, Bowditch volume 2, plotting sheets, and a starfinder, dividers, parallel rules, triangles, and a calculator.

I will also show you how to do sailing problems:
1. Great Circle
2. Mercator
3. Parallel
4. Mid-Latitude

Also included in this site will be Terrestial exam questions:

1. Compass problems with Leeway
2. Finding Deviation or Gyro error on a Range
3. Compass deviation table problems
4. Computing the Visibility of a light
5. Distance off by two bearings
6. Finding a course to steer with a known set and drift
7. Radar plotting problems
8. Computing the height of the tide
9. Computing the velocity of the tidal current
10. Fuel consumption
11. Speed by RPM
12. Zone time calculations

This site will be updated and is under construction.

Local Apparent Noon Problem #1

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Local Apparent Noon Problem #2

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How to Determine your Latitude by Local Apparent Noon (LAN)

The objective of this is to define how to compute a latitude line by using the sun at Local Apparent Noon (LAN).
Since the latitude of a position may be determined by finding the distance between the equinoctial and the zenith, you only need to know the declination and zenith distance (coaltitude) of a body to determine latitude. This has been used by mariners for centuries because of it's simplicity.

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Azimuth Exam Questions (Sun, Stars, Planets)

Azimuth Sun Only
On 31 May 1981, your vessel's 1420 zone time DR position is Lat. 29° 06.0' N, Long. 120° 06.0' W, when an azimuth of the Sun is observed. The bearing of the Sun per standard magnetic compass was 255.3°. The chronometer time of the observation is 10h 17m 24s. The chronometer error is 02m 32s slow. The variation for this area is 12.9° E. What is the deviation of the standard magnetic compass?
A. 2.5° W
B. 2.9° W
C. 2.9° E
D. 3.2° E

On 7 December 1981, your vessel's 0835 zone time DR position is Lat. 28° 30.0' N, Long. 125° 39.3' W, when an azimuth of the Sun is observed. The chronometer time of the sight is 04h 34m 48s, and Sun is bearing 113° per standard compass. The chronometer error 01 m 24s slow, and the variation in the area is 13.0 E. What is the deviation of the standard compass?
A. 0.5° E
B. 1.0° W
C. 2.5° E
D. 3.0° W

Azimuth Stars Only
On 16 June 1981, your 0430 zone time DR position is Lat. 29° 24.0' S, Long. 36° 16.0' E. At that time, you observe Vega bearing 341.0° psc. The chronometer reads 02h 32m 06s, and the chronometer error is 01 m 54s fast. The variation is 20.5° W. What is the deviation?
A. 3.2° E
B. 3.2° W
C. 2.4° W
D. 2.8° E

On 15 October 1981, your 0325 zone time DR position is Lat. 26° 51.0' N, Long. 138° 17.0' W. At that time, you observe Canopus bearing 167° pgc. The chronometer reads 00h 25m 36s, and the chronometer error is 00m 20s slow. The variation is 2° E. What is the gyro error?
A. 1.3° W
B. 3.2° W
C. 3.2° E
D. 4.1° W

Azimuth Planets Only
On 6 October 1981, your0416 zone time DR position is Lat. 25° 16.0' N, Long. 130° 25.0' E At that time, you observe Mars bearing 083° psc. The chronometer reads 07h 16m 22s, and the chronometer error is 00m 10s fast. The variation is 1.5° E. What is the deviation of the standard compass?
A. 0.4° E
B. 1.2° W
C. 3.5° E
D. 19.0 E

At 2326 ZT, on 22 June 1981, your vessel's position IS Lat. 28° 30.0' N, LONG 150° 04.0' W. An azimuth of the planet Jupiter is observed, and the standard compass bearing is 250.4° psc. The chronometer reads 09h 24m 36s and is 01m 12s slow. The variation of this area is 13.5° E. What is the deviation of the standard compass?
A. 3.0° W
B. 3.5° W
C. 1.5° E
D. 2.3° E

Azimuth of the Sun

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Azimuth of the Sun (short method)

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