RYA Yachtmaster Celestial Navigation Basics

Question 1

What is the purpose of celestial navigation in the context of the Yachtmaster Offshore syllabus?

Accepted Answer

To provide a backup position-fixing method when GPS is unavailable, using the Sun's altitude and the Nautical Almanac

Answer

To replace GPS in all offshore passages

Answer

To measure the depth of water using star altitudes

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To calculate compass variation using star bearings alone

Question 2

The 'sextant' is used in celestial navigation to measure:

Accepted Answer

The altitude of a celestial body above the visible horizon

Answer

The magnetic variation at sea

Answer

The vessel's latitude by measuring sea depth

Answer

The angular distance between two headlands

Question 3

The Nautical Almanac provides which information for celestial navigation?

Accepted Answer

The Greenwich Hour Angle (GHA) and Declination of celestial bodies for every hour of every day

Answer

Only sunrise and sunset times

Answer

Tidal predictions for ocean ports

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Magnetic variation for all oceans

Question 4

What is 'declination' of the Sun as used in celestial navigation?

Accepted Answer

The angular distance of the Sun north or south of the celestial equator — equivalent to latitude on the celestial sphere

Answer

The difference between True North and Magnetic North

Answer

The bearing of the Sun at noon

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The altitude of the Sun at sunrise

Question 5

A noon sight of the Sun gives a latitude line because:

Accepted Answer

At local apparent noon, the Sun is on the observer's meridian — its maximum altitude gives latitude directly

Answer

The Sun is always due North at noon

Answer

Noon is the only time the horizon is visible

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The Almanac only gives noon values

Question 6

The 'intercept method' (Marcq St. Hilaire) in celestial navigation involves:

Accepted Answer

Comparing the calculated altitude of a body from an assumed position to the observed altitude, to find the distance and direction of the position line from the assumed position

Answer

Measuring the angle between two bodies

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Calculating longitude from the Moon's altitude

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Comparing compass and celestial bearings to find deviation