horizontal parallax

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horizontal parallax

The astronomer measures the horizontal parallax of the moon.

Definition
  1. Noun:
    • The maximum parallax observed when a celestial body is at the horizon: In astronomy, this is the difference in the apparent position of an object (like the moon or a planet) when viewed from two different points, specifically when the object is on the observer's horizon. It represents the largest possible parallax for that body from a given observation point on Earth.
Usage
  • This term is used in precise astronomical observation and calculation.
  • It is a specific measurement used to determine distances to celestial bodies.
  • The concept is fundamental in celestial navigation and geodesy.
Examples
  • Noun:
    • The horizontal parallax of the Moon is used to calculate its precise distance from Earth.
    • Accurate tables of the sun's horizontal parallax were essential for 19th-century navigators.
Advanced Usage
  • "To correct for horizontal parallax": A standard procedure in astronomy to adjust observational data for this effect to obtain true celestial coordinates.
    • Before calculating the eclipse's path, the astronomer corrected the measurements for horizontal parallax.
Variants and Related Words
  • Parallax (n): The general effect or the apparent displacement of an observed object due to a change in the observer's position.
    • Stellar parallax is used to measure the distance to nearby stars.
  • Diurnal Parallax (n): The daily parallax of a celestial body due to Earth's rotation, of which horizontal parallax is the maximum value.
    • Diurnal parallax is greatest for objects on the celestial horizon.
Synonyms
  • Geocentric Parallax: Often used interchangeably, though geocentric parallax can refer more broadly to parallax measurements from the center of the Earth.
  • Equatorial Horizontal Parallax: A more specific term denoting the horizontal parallax when the observer is at the Earth's equator.
Related Concepts (Not Phrasal Verbs or Idioms)
  • Parallax Angle: The angle of the parallax shift.
  • Solar Parallax: Specifically, the horizontal parallax of the Sun.
  • Lunar Parallax: Specifically, the horizontal parallax of the Moon.
horizontal parallax

The astronomer measures the horizontal parallax of the moon.

Noun
  1. the maximum parallax observed when the celestial body is at the horizon