Astronomy for surveying – condition for a star to culminate at the zenith In practical field astronomy, a star will culminate exactly at the zenith of an observing station if its declination has which relationship with the station’s latitude?

Introduction / Context:
Surveyors use astronomical observations to determine direction, time, and geographic position. Understanding the relationship between a star’s declination and the observer’s latitude helps predict where the star will pass on the celestial sphere, including when it passes directly overhead at the zenith.

Given Data / Assumptions:

• Declination (δ) is measured north or south of the celestial equator.
• Latitude (φ) locates the observer on Earth.
• Culmination refers to the star’s transit across the local meridian.

Concept / Approach:
At upper culmination on the local meridian, the star’s altitude equals 90° when it is at the zenith. The well-known relationship is: altitude at meridian passage = 90° − |φ − δ| for a circumpolar or suitably positioned star. For the altitude to be exactly 90°, we need |φ − δ| = 0, i.e., δ = φ.

Step-by-Step Solution:
Use altitude at meridian: H = 90° − |φ − δ|.Set H = 90° for zenith culmination → |φ − δ| = 0.Therefore δ must equal φ.

Verification / Alternative check:
Textbook celestial triangles confirm that when the star’s declination matches the observer’s latitude, the zenith lies on the star’s meridian circle at culmination.

Why Other Options Are Wrong:

• Longitude does not directly determine zenith culmination.
• “Less than latitude” is insufficient; equality is required for exact zenith passage.
• “None” is invalid because a clear condition exists.

Common Pitfalls:
Confusing azimuth with altitude; culmination refers to crossing the meridian (maximum altitude), not direction around the horizon.

Final Answer:
Equal to the latitude of the place