How to successfully complete Celestial Navigation Calculations

You will learn how to calculate the Greenwich Hour Angle (GHA), Local Hour Angle (LHA) and Declination for the Sun, Stars and Planets using the Nautical Almanac.

You will learn how to calculate Altitudes, Azimuths and True Bearings of celestial bodies. You will also learn how to calculate an amplitude of the Sun when it is rising and setting.

You will also learn how to fix the ship’s position using position lines from observations from celestial objects.

This online training for Deck Cadets is aligned with the Standards of Training, Certification and Watchkeeping (STCW) and the UK MCA / Scottish Qualifications Authority (SQA) Level 7 Celestial Navigation unit.

This learning can be used to study and prepare for the Celestial Navigation assessment.

You can see the contents of what is contained in this unit in the contents list below, and subscribe here.

1. Greenwich Hour Angle (GHA)
   1. Subscriber Content
2. Calculating the GHA, LHA and Declination of the Sun
3. Calculating the GHA, LHA and Declination of Planets
4. Calculating the GHA, SHA and Declination of Stars
5. Observed and True Altitudes
6. Calculating the Azimuth and True Bearing of a Celestial Body
7. Polaris
8. Amplitudes of the Sun when Rising and Setting
9. Position Lines and Fixes
10. Marine Chronometer and Time Corrections
11. Local Mean Time
12. How to Calculate Local Time
13. How to Calculate UTC
14. The Nautical Almanac and GMT
15. The Marine Sextant
16. The Errors of a Marine Sextant
17. Using a Marine Sextant
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We need the Greenwich Hour Angle (GHA), Local Hour Angle (LHA) and Declination to do our calculations and eventually find our latitude and longitude.

Greenwich Hour Angle (GHA)

The GHA of the body is the angle between Greenwich and the celestial body. It is always measured from Greenwich in a Westerly (clockwise) direction.

GHA is listed in the nautical almanac. It is different for each celestial body.

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