minute of arc

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minute of arc

An astronomer uses a telescope to measure a minute of arc in the night sky.

Definition
  1. Noun:
    • A unit of angular measurement: A "minute of arc" is a specific unit for measuring angles. It is defined as one sixtieth (1/60) of one degree of angular measurement. This unit is used in fields like astronomy, navigation, and cartography to express precise angles or coordinates.
Examples of Usage
  • Noun:
    • The telescope's pointing accuracy is within one minute of arc. (The telescope can be aimed with an error smaller than 1/60th of a degree.)
    • The difference in their latitude was calculated to be five minutes of arc. (The north-south distance between them was equivalent to 5/60ths of a degree.)
Advanced Usage

  • "Arcminute": This is a common synonym and contraction of "minute of arc". It is frequently used in technical contexts.

    • The apparent size of the planet is 30 arcminutes. (The planet appears to span an angle of 30 sixtieths of a degree in the sky.)

  • Symbol (' ): A minute of arc is often represented by a prime symbol ('). For example, 15' is read as "fifteen minutes of arc" or "fifteen arcminutes".

    • The coordinates are 45° 30' N. (The coordinates are forty-five degrees and thirty minutes of arc North.)
Variants and Related Words
  • Arcminute (n): A direct synonym for "minute of arc".
  • Second of arc / Arcsecond (n): A smaller unit of angular measurement, equal to 1/60th of a minute of arc (or 1/3600th of a degree). Its symbol is (").
Synonyms
  • Arcminute: The most common direct synonym.
  • MOA: An abbreviation (Minute Of Angle) commonly used in firearm and ballistics contexts to describe the accuracy of a weapon or scope. (Note: In this specific technical field, "minute of angle" is functionally equivalent to "minute of arc" for practical measurements on Earth.)
Related Phrases
  • Minute of angle (MOA): While mathematically identical to a minute of arc, this term is specifically used in shooting sports to describe shot group dispersion or scope adjustments. It is a contextual variant.
    • The rifle is capable of one MOA accuracy. (The rifle can consistently hit within a one-minute-of-arc circle at a given distance.)
minute of arc

An astronomer uses a telescope to measure a minute of arc in the night sky.

Noun
  1. a unit of angular distance equal to a 60th of a degree

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