NN310 – CELESTIAL NAVIGATION | EXAM QUESTIONS AND CORRECT
ANSWERS | VERIFIED MARITIME CELESTIAL NAVIGATION LATEST
VERSION 2026/2027
Q1: What is celestial navigation?
A1: Celestial navigation is the practice of determining a vessel's position
on Earth by observing and measuring the angular distances of celestial
bodies (sun, moon, stars, planets) above the horizon.
Q2: What is the Celestial Sphere?
A2: An imaginary sphere of infinite radius concentric with the Earth, upon
which all celestial bodies appear to be projected.
Q3: What is the Celestial Equator?
A3: The great circle on the celestial sphere formed by projecting Earth's
equator onto the celestial sphere; also called the equinoctial.
Q4: What are the Celestial Poles?
A4: The points on the celestial sphere where Earth's axis of rotation
intersects it — the North Celestial Pole (near Polaris) and South Celestial
Pole.
Q5: What is Declination (Dec)?
A5: The angular distance of a celestial body north or south of the celestial
equator, measured along the hour circle of the body (0°–90° N or S).
Analogous to latitude.
Q6: What is Greenwich Hour Angle (GHA)?
,A6: The angular distance measured westward along the celestial equator
from the Greenwich meridian (prime meridian projected) to the hour
circle of a celestial body (0°–360°).
Q7: What is Local Hour Angle (LHA)?
A7: The angular distance measured westward along the celestial equator
from the observer's local meridian to the hour circle of a celestial body
(0°–360°). LHA = GHA ± Longitude.
Q8: What is Sidereal Hour Angle (SHA)?
A8: The angular distance measured westward along the celestial equator
from the First Point of Aries (Vernal Equinox) to the hour circle of a star
(0°–360°). Used for stars in the Nautical Almanac.
Q9: What is the relationship between GHA, SHA, and GHA Aries?
A9: GHA Star = GHA Aries + SHA Star.
Q10: What is Right Ascension (RA)?
A10: The angular distance measured eastward along the celestial equator
from the First Point of Aries to the hour circle of a celestial body. Usually
expressed in hours (0h–24h). RA = 360° – SHA.
Q11: What is the Ecliptic?
A11: The great circle on the celestial sphere representing the apparent
annual path of the Sun among the stars, inclined at about 23.5° to the
celestial equator.
Q12: What is the Obliquity of the Ecliptic?
A12: The angle between the ecliptic and the celestial equator,
approximately 23° 26' (varies slightly over time).
,Q13: What are the Equinoxes?
A13: The two points where the ecliptic crosses the celestial equator —
Vernal Equinox (First Point of Aries, ~March 21) and Autumnal Equinox
(~September 23).
Q14: What are the Solstices?
A14: The points on the ecliptic where the Sun reaches its maximum
declination north or south of the celestial equator — Summer Solstice
(~June 21) and Winter Solstice (~December 22).
Q15: What is the Zenith?
A15: The point on the celestial sphere directly above the observer on
Earth.
Q16: What is the Nadir?
A16: The point on the celestial sphere directly below the observer,
diametrically opposite the zenith.
Q17: What is the Observer's Meridian?
A17: The great circle on the celestial sphere passing through the
observer's zenith, the celestial poles, and the nadir.
Q18: What is an Hour Circle?
A18: A great circle on the celestial sphere passing through a celestial body
and both celestial poles.
Q19: What is the Prime Vertical?
A19: The great circle on the celestial sphere passing through the
observer's zenith, the east and west points of the horizon, and the nadir.
Q20: What is Altitude?
, A20: The angular distance of a celestial body measured above the horizon
along a vertical circle, from 0° (horizon) to 90° (zenith).
Q21: What is Zenith Distance (z)?
A21: The angular distance from the observer's zenith to the celestial body,
measured along a vertical circle. z = 90° – Altitude.
Q22: What is Azimuth?
A22: The horizontal direction of a celestial body measured from true
north clockwise through 360° (or from N or S toward E or W in quadrant
notation).
Q23: What is Amplitude?
A23: The angular distance of a celestial body from the prime vertical (east
or west) measured along the horizon at the moment of rising or setting.
Q24: What is the Geographic Position (GP) of a celestial body?
A24: The point on Earth's surface directly below a celestial body, where a
line from the body to Earth's center intersects the surface. Latitude =
Declination; Longitude = GHA (west) or 360° – GHA (east).
Q25: What is a Position Circle (Circle of Equal Altitude)?
A25: A circle on Earth's surface, centered at the geographic position of a
celestial body, on which all observers measure the same altitude of that
body at the same instant.
Q26: What is the PZX (Navigational) Triangle?
A26: The spherical triangle on the celestial sphere formed by the elevated
pole (P), the observer's zenith (Z), and the celestial body (X). Used as the
basis for sight reduction.
ANSWERS | VERIFIED MARITIME CELESTIAL NAVIGATION LATEST
VERSION 2026/2027
Q1: What is celestial navigation?
A1: Celestial navigation is the practice of determining a vessel's position
on Earth by observing and measuring the angular distances of celestial
bodies (sun, moon, stars, planets) above the horizon.
Q2: What is the Celestial Sphere?
A2: An imaginary sphere of infinite radius concentric with the Earth, upon
which all celestial bodies appear to be projected.
Q3: What is the Celestial Equator?
A3: The great circle on the celestial sphere formed by projecting Earth's
equator onto the celestial sphere; also called the equinoctial.
Q4: What are the Celestial Poles?
A4: The points on the celestial sphere where Earth's axis of rotation
intersects it — the North Celestial Pole (near Polaris) and South Celestial
Pole.
Q5: What is Declination (Dec)?
A5: The angular distance of a celestial body north or south of the celestial
equator, measured along the hour circle of the body (0°–90° N or S).
Analogous to latitude.
Q6: What is Greenwich Hour Angle (GHA)?
,A6: The angular distance measured westward along the celestial equator
from the Greenwich meridian (prime meridian projected) to the hour
circle of a celestial body (0°–360°).
Q7: What is Local Hour Angle (LHA)?
A7: The angular distance measured westward along the celestial equator
from the observer's local meridian to the hour circle of a celestial body
(0°–360°). LHA = GHA ± Longitude.
Q8: What is Sidereal Hour Angle (SHA)?
A8: The angular distance measured westward along the celestial equator
from the First Point of Aries (Vernal Equinox) to the hour circle of a star
(0°–360°). Used for stars in the Nautical Almanac.
Q9: What is the relationship between GHA, SHA, and GHA Aries?
A9: GHA Star = GHA Aries + SHA Star.
Q10: What is Right Ascension (RA)?
A10: The angular distance measured eastward along the celestial equator
from the First Point of Aries to the hour circle of a celestial body. Usually
expressed in hours (0h–24h). RA = 360° – SHA.
Q11: What is the Ecliptic?
A11: The great circle on the celestial sphere representing the apparent
annual path of the Sun among the stars, inclined at about 23.5° to the
celestial equator.
Q12: What is the Obliquity of the Ecliptic?
A12: The angle between the ecliptic and the celestial equator,
approximately 23° 26' (varies slightly over time).
,Q13: What are the Equinoxes?
A13: The two points where the ecliptic crosses the celestial equator —
Vernal Equinox (First Point of Aries, ~March 21) and Autumnal Equinox
(~September 23).
Q14: What are the Solstices?
A14: The points on the ecliptic where the Sun reaches its maximum
declination north or south of the celestial equator — Summer Solstice
(~June 21) and Winter Solstice (~December 22).
Q15: What is the Zenith?
A15: The point on the celestial sphere directly above the observer on
Earth.
Q16: What is the Nadir?
A16: The point on the celestial sphere directly below the observer,
diametrically opposite the zenith.
Q17: What is the Observer's Meridian?
A17: The great circle on the celestial sphere passing through the
observer's zenith, the celestial poles, and the nadir.
Q18: What is an Hour Circle?
A18: A great circle on the celestial sphere passing through a celestial body
and both celestial poles.
Q19: What is the Prime Vertical?
A19: The great circle on the celestial sphere passing through the
observer's zenith, the east and west points of the horizon, and the nadir.
Q20: What is Altitude?
, A20: The angular distance of a celestial body measured above the horizon
along a vertical circle, from 0° (horizon) to 90° (zenith).
Q21: What is Zenith Distance (z)?
A21: The angular distance from the observer's zenith to the celestial body,
measured along a vertical circle. z = 90° – Altitude.
Q22: What is Azimuth?
A22: The horizontal direction of a celestial body measured from true
north clockwise through 360° (or from N or S toward E or W in quadrant
notation).
Q23: What is Amplitude?
A23: The angular distance of a celestial body from the prime vertical (east
or west) measured along the horizon at the moment of rising or setting.
Q24: What is the Geographic Position (GP) of a celestial body?
A24: The point on Earth's surface directly below a celestial body, where a
line from the body to Earth's center intersects the surface. Latitude =
Declination; Longitude = GHA (west) or 360° – GHA (east).
Q25: What is a Position Circle (Circle of Equal Altitude)?
A25: A circle on Earth's surface, centered at the geographic position of a
celestial body, on which all observers measure the same altitude of that
body at the same instant.
Q26: What is the PZX (Navigational) Triangle?
A26: The spherical triangle on the celestial sphere formed by the elevated
pole (P), the observer's zenith (Z), and the celestial body (X). Used as the
basis for sight reduction.
