# If ‘δ’ is the declination of the star and ‘φ’ is the latitude of the observer then the hour angle of the star at elongation is given by

A. sin H = tan φ . cot δ

B. cos H = tan φ . cot δ

C. tan H = tan φ . cot δ

D. None of these

**Answer: Option B **

**The sidereal day is the time interval between two successive upper transits of**

A. Mean sun

B. First point of Aries

C. First point of Libra

D. The polar star

**The angle of intersection of the two plane mirrors of an optical square is**

A. 30°

B. 45°

C. 60°

D. 90°

**Which of the following statements is incorrect ?**

A. Error due to refraction may not be completely eliminated by reciprocal levelling.

B. Tilting levels are commonly used for precision work.

C. The last reading of levelling is always a foresight.

D. All of the above statements are incorrect.

**Right ascension of a heavenly body is its equatorial angular distance measured**

A. Westward from the first point of Libra

B. Eastward from the first point of Aeries

C. Westward from the first point of Aeries

D. Eastward from the first point of Libra

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