Question

In the context of planetary parallax and eclipse calculations, what is the orientation/direction of the 'Nati' (Parallax in Latitude)?

• A. Yamya-uttara (North-South)
• B. Purva-apara (East-West)
• C. Urdhva-adhara (Up-Down)
• D. Koniya (Angular/Diagonal)

Hint:

Remember: Lambana = Longitude = East/West. Nati = Latitude = North/South. In Sanskrit, Latitude is often associated with the North-South (Yamya-Uttara) axis.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Parallax (Lambana) is the apparent displacement of a celestial body when viewed from the surface of the Earth instead of the center of the Earth. In Indian astronomy, this parallax is resolved into two perpendicular components relative to the Ecliptic (the Sun's path):
1. Lambana: Parallax in Longitude (East-West along the ecliptic).
2. Nati: Parallax in Latitude (North-South perpendicular to the ecliptic).

Step 2: Detailed Explanation of 'Nati':
'Nati' specifically refers to the depression of the Moon's position toward the South or North due to the observer's terrestrial latitude.
- Since the ecliptic is the primary reference line for eclipses, any displacement perpendicular to this line is considered a change in latitude.
- The word 'Yamya' means South and 'Uttara' means North. Therefore, 'Yamya-uttara' signifies the meridional or North-South direction.
- During a solar eclipse, the Nati is calculated to determine if the Moon's disk will actually overlap with the Sun's disk from the observer's specific location. If the Nati is too large, the eclipse may be partial or invisible even if the longitudes match.

Step 3: Reasoning for Option (A):
The displacement 'Lambana' is along the 'Purva-apara' (East-West) direction because it affects the *time* of the eclipse (longitude). The displacement 'Nati' is along the 'Yamya-uttara' (North-South) direction because it affects the *magnitude* of the eclipse (latitude). This distinction is fundamental to the 'Graha-Yuti' (conjunction) and 'Grahana' (eclipse) chapters of Siddhantic texts.

Step 4: Final Answer:
The direction of Nati is Yamya-uttara (North-South).