In Field Astronomy, consider the following statements regarding the Celestial Sphere 1. The Zenith and Nadir are the points where the plumb line at the observer's station, if produced, meets the celestial sphere. 2. The Azimuth of a heavenly body is the arc of the horizon intercepted between the observer’s meridian and the vertical circle passing through the body. 3. The Declination of a star is analogous to the longitude on the Earth's surface. Which of the statements given above are correct?
- A1 and 2 onlyCorrect
- B2 and 3 only
- C1 and 3 only
- D1, 2 and 3
Solution
Concept
Celestial Sphere and Field Astronomy Concepts
Formula
N/A
Step-by-step solution
1. Verify Statements 1 and 2, which correctly define Zenith, Nadir, and Azimuth in field astronomy. 2. Note that Statement 3 is incorrect because Declination is analogous to latitude, not longitude. 3. Select Option (a) as only Statements 1 and 2 are correct.
Explanation
Option A is correct because statements 1 and 2 are accurate definitions in field astronomy. The Zenith (directly overhead) and Nadir (directly below) are defined by extending the observer's plumb line to the celestial sphere, and Azimuth measures the horizontal angle along the horizon from the meridian to the body's vertical circle. Statement 3 is incorrect because Declination is analogous to latitude on Earth, not longitude (Right Ascension is analogous to longitude).
Shortcut
To easily remember Celestial Sphere concepts, use these simple memory rules: - Plumb Line Points: Zenith points straight Up (overhead), Nadir points straight Down (underfoot). - Coordinate Analogies: Declination (Dec) maps to Latitude (both measure angular distance north/south of the equator), while Right Ascension (RA) maps to Longitude. - Azimuth: Think "Azimuth = Angle on Horizon" — it is the horizontal bearing measured along the horizon.
Common mistake
A common mistake is selecting Option D by incorrectly assuming that Declination corresponds to longitude on the Earth's surface. In field astronomy, Declination is analogous to latitude, while Right Ascension is analogous to longitude. Confusing these two coordinate analogies leads students to consider Statement 3 correct.
Correct answer: A) 1 and 2 only