Fundamentals of astronomical terms in surveying: The angular distance of a celestial (heavenly) body from the celestial equator, measured along the meridian through that body, is called what?

Introduction / Context:
Surveyors use basic astronomical quantities to determine latitude, azimuth, and time. One of the most important is the angular position of a celestial body relative to the celestial equator, measured along the body’s meridian. Recognizing the correct term ensures you apply the right formulas in astronomical observations for positioning.

Given Data / Assumptions:

• Celestial sphere model is used.
• The meridian is the great circle through the observer’s zenith and the celestial poles.
• We measure angles along great circles unless noted.

Concept / Approach:
Declination (δ): angular distance of a body north (+) or south (−) of the celestial equator, measured along the body’s hour circle (its meridian).Altitude (h): angle of the body above the observer’s horizon.Zenith distance (z): angle from zenith to the body, so z = 90° − h.Co-latitude: 90° − latitude (useful in some spherical triangle relations).

Step-by-Step Solution:
Identify the phrase “from the equator, measured along its meridian.”This exactly matches the definition of declination.Therefore, the correct term is “Declination.”

Verification / Alternative check:
In spherical astronomy, right ascension is measured along the celestial equator from the First Point of Aries, not along the body’s meridian; altitude/zenith distance reference the local horizon/zenith, not the celestial equator.

Why Other Options Are Wrong:
Altitude/Zenith distance: horizon/zenith based, not equator-based.Co-latitude: observer-related constant, not a body’s coordinate.Right ascension: measured on the equator, not along the body’s meridian.

Common Pitfalls:
Confusing declination with altitude; altitude changes rapidly with time and location, while declination is fixed for a star (ignoring precession/nutation) at a given epoch.

Final Answer:
Declination.