ASA 107 – Celestial Navigation Exam
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Answers,Plus Rationales/Expert
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1. The main purpose of celestial navigation is to
a) Determine latitude only
b) Determine longitude only
c) Determine position using celestial bodies
d) Determine compass deviation
c) Determine position using celestial bodies
Rationale: Celestial navigation uses measurements of celestial bodies (sun, moon,
planets, stars) to calculate both latitude and longitude.
2. A sextant is used to measure
a) Azimuth of a star
b) Altitude of a celestial body above the horizon
c) Compass variation
d) Time of meridian passage
b) Altitude of a celestial body above the horizon
Rationale: The sextant measures the angle between a celestial body and the visible
horizon.
3. The line of position (LOP) obtained from a sextant sight is
a) A straight line on the Earth’s surface
b) A great circle through the body
c) A small circle on the Earth’s surface
d) A rhumb line parallel to the equator
c) A small circle on the Earth’s surface
Rationale: An LOP is part of a circle of equal altitude around the geographical
position of the body.
,4. Greenwich Mean Time (GMT) is the same as
a) Local Apparent Noon
b) Universal Time Coordinated (UTC)
c) Local Mean Time
d) Sidereal Time
b) Universal Time Coordinated (UTC)
Rationale: For navigation purposes, GMT is effectively the same as UTC.
5. The Geographical Position (GP) of a celestial body is defined as
a) The observer’s assumed position
b) The latitude and longitude directly beneath the celestial body
c) The line of position
d) The altitude of the star
b) The latitude and longitude directly beneath the celestial body
Rationale: GP is the point on Earth where the celestial body is at zenith.
6. The local hour angle (LHA) is calculated from
a) Declination and altitude
b) GHA and longitude
c) SHA and latitude
d) GMT and azimuth
b) GHA and longitude
Rationale: LHA = GHA ± longitude depending on east or west longitude.
7. A meridian passage occurs when
a) The body crosses the prime meridian
b) The body crosses the observer’s meridian
c) The body crosses the celestial equator
d) The body reaches its maximum azimuth
b) The body crosses the observer’s meridian
Rationale: Meridian passage is when a celestial body is directly north or south of
the observer.
8. A noon sight is primarily used to determine
a) Latitude
b) Longitude
c) Variation
d) Azimuth
a) Latitude
Rationale: At Local Apparent Noon, the sun’s maximum altitude allows latitude to
be determined easily.
, 9. The declination of a celestial body is comparable to
a) Longitude
b) Latitude
c) Altitude
d) Azimuth
b) Latitude
Rationale: Declination measures angular distance north or south of the celestial
equator, just like latitude on Earth.
10. The sidereal hour angle (SHA) is used mainly for
a) Planets
b) The moon
c) Fixed stars
d) The sun
c) Fixed stars
Rationale: SHA is tabulated for stars to simplify celestial calculations.
11. Which publication provides daily positions of celestial bodies?
a) The Almanac of Astronomy
b) The Nautical Almanac
c) The Pilot Charts
d) The Bowditch Tables
b) The Nautical Almanac
Rationale: The Nautical Almanac gives daily GHA and declination for navigational
bodies.
12. Time zones are based on
a) Every 10° of longitude
b) Every 15° of longitude
c) Every 20° of longitude
d) Arbitrary political boundaries only
b) Every 15° of longitude
Rationale: The Earth rotates 15° per hour, so time zones are based on 15°
increments.
13. The altitude intercept method is also called
a) Marcq St. Hilaire method
b) HO 229 method
c) Time sight method
d) Ex-meridian method
a) Marcq St. Hilaire method
Rationale: This is the most common method of sight reduction today.
With Actual Questions & Verified
Answers,Plus Rationales/Expert
Verified For Guaranteed Pass
2025/2026 /Latest Update/Instant
Download Pdf
1. The main purpose of celestial navigation is to
a) Determine latitude only
b) Determine longitude only
c) Determine position using celestial bodies
d) Determine compass deviation
c) Determine position using celestial bodies
Rationale: Celestial navigation uses measurements of celestial bodies (sun, moon,
planets, stars) to calculate both latitude and longitude.
2. A sextant is used to measure
a) Azimuth of a star
b) Altitude of a celestial body above the horizon
c) Compass variation
d) Time of meridian passage
b) Altitude of a celestial body above the horizon
Rationale: The sextant measures the angle between a celestial body and the visible
horizon.
3. The line of position (LOP) obtained from a sextant sight is
a) A straight line on the Earth’s surface
b) A great circle through the body
c) A small circle on the Earth’s surface
d) A rhumb line parallel to the equator
c) A small circle on the Earth’s surface
Rationale: An LOP is part of a circle of equal altitude around the geographical
position of the body.
,4. Greenwich Mean Time (GMT) is the same as
a) Local Apparent Noon
b) Universal Time Coordinated (UTC)
c) Local Mean Time
d) Sidereal Time
b) Universal Time Coordinated (UTC)
Rationale: For navigation purposes, GMT is effectively the same as UTC.
5. The Geographical Position (GP) of a celestial body is defined as
a) The observer’s assumed position
b) The latitude and longitude directly beneath the celestial body
c) The line of position
d) The altitude of the star
b) The latitude and longitude directly beneath the celestial body
Rationale: GP is the point on Earth where the celestial body is at zenith.
6. The local hour angle (LHA) is calculated from
a) Declination and altitude
b) GHA and longitude
c) SHA and latitude
d) GMT and azimuth
b) GHA and longitude
Rationale: LHA = GHA ± longitude depending on east or west longitude.
7. A meridian passage occurs when
a) The body crosses the prime meridian
b) The body crosses the observer’s meridian
c) The body crosses the celestial equator
d) The body reaches its maximum azimuth
b) The body crosses the observer’s meridian
Rationale: Meridian passage is when a celestial body is directly north or south of
the observer.
8. A noon sight is primarily used to determine
a) Latitude
b) Longitude
c) Variation
d) Azimuth
a) Latitude
Rationale: At Local Apparent Noon, the sun’s maximum altitude allows latitude to
be determined easily.
, 9. The declination of a celestial body is comparable to
a) Longitude
b) Latitude
c) Altitude
d) Azimuth
b) Latitude
Rationale: Declination measures angular distance north or south of the celestial
equator, just like latitude on Earth.
10. The sidereal hour angle (SHA) is used mainly for
a) Planets
b) The moon
c) Fixed stars
d) The sun
c) Fixed stars
Rationale: SHA is tabulated for stars to simplify celestial calculations.
11. Which publication provides daily positions of celestial bodies?
a) The Almanac of Astronomy
b) The Nautical Almanac
c) The Pilot Charts
d) The Bowditch Tables
b) The Nautical Almanac
Rationale: The Nautical Almanac gives daily GHA and declination for navigational
bodies.
12. Time zones are based on
a) Every 10° of longitude
b) Every 15° of longitude
c) Every 20° of longitude
d) Arbitrary political boundaries only
b) Every 15° of longitude
Rationale: The Earth rotates 15° per hour, so time zones are based on 15°
increments.
13. The altitude intercept method is also called
a) Marcq St. Hilaire method
b) HO 229 method
c) Time sight method
d) Ex-meridian method
a) Marcq St. Hilaire method
Rationale: This is the most common method of sight reduction today.
