sextant

/'sekstənt/

Thân thiện

A sailor uses a sextant to measure the sun's angle above the horizon.

Definition

1. Noun:
   • A measuring instrument for navigation: A sextant is an optical instrument used to measure the angular distance between two visible objects, most commonly the angle between a celestial body (like the sun or a star) and the horizon. This measurement is crucial for determining latitude and longitude at sea.
   • A unit of angular measure: In mathematics, a sextant is an arc or angle equal to one-sixth of a circle, or 60 degrees.

Examples

• Noun (Instrument):
  • The sailor used a sextant to determine the ship's position by measuring the angle of the sun above the horizon.
  • Before GPS, navigators relied heavily on the accuracy of their sextants for ocean voyages.
• Noun (Angular Unit):
  • The ancient circle was divided into six equal sextants.
  • An angle of one sextant is equivalent to 60 degrees.

Advanced Usage

• "To take a sextant reading": The act of using the instrument to measure an angle.
  • The captain went on deck at noon to take a sextant reading of the sun.
• "Bubble sextant": A specific type of sextant that uses an artificial horizon (a bubble level) for use in aircraft or when a natural horizon is not visible.
  • The pilot used a bubble sextant for celestial navigation during the long flight.

Variants and Related Words

• Sextantal (adj): Pertaining to or resembling a sextant or a sextant's arc.
  • The sextantal division of the circle is an ancient concept.
• Octant (n): A similar navigational instrument for measuring angles up to 90 degrees (one-eighth of a circle).

Synonyms

• Navigational instrument: A general term for tools like the sextant, astrolabe, and compass.
• Angle measurer: A descriptive term for the instrument's primary function.

Related Phrases

• "Shoot the sun" / "Shoot a star": Informal phrases for using a sextant to measure the altitude of a celestial body.
  • At dusk, the navigator prepared to shoot the stars with his sextant.

Học thuật

Noun

1. a measuring instrument for measuring the angular distance between celestial objects; resembles an octant
2. a unit of angular distance equal to 60 degrees