Celestial Coordinate System and Indian Calendaring Mechanisms

Overview

• The lecture explores the basics of the celestial coordinate system and how it relates to Indian calendaring systems.
• Focus on the concept of a year and sidereal periods.

Key Concepts

Sidereal Period

• Definition: The time taken by an object to complete one revolution in the background of stars.
  • Example: Sidereal period of the Sun involves completing one loop around the ecliptic.
  • Moon's sidereal period is approximately 27.32 days, constituting a lunar cycle.

Division of the Zodiac

• The zodiac is divided into 27 equal parts starting from a fixed initial point in the ecliptic.
• Each part corresponds to the moon’s trajectory.
• Nakshatra:
  • Each of the 27 divisions is called a nakshatra.
  • Each division spans 13 degrees and 20 minutes of arc.
  • Named after a prominent star in its segment.
• 27 Nakshatras are mapped onto 12 Rāśis, with each Rāśi containing 2 and a quarter nakshatra.

Sources

• The list of 27 nakshatras and their names are found in the Taittiriya Samhita and Atharva Veda.

Calendrical Systems

Solar Calendar

• Based on the solar year, defined by the time taken for the sun to complete one revolution around the ecliptic.
• Followed in several Indian states like Tripura, Assam, Bengal, Orissa, Tamil Nadu, Kerala, Punjab, and Haryana.

Lunar Calendar

• Based on the lunar year, determined by the period from one full moon to the next or one new moon to the next.
• Consists of 12 lunar months.
• Used for determining religious festival dates and auspicious times in all Indian states.

Luni-Solar Calendar

• Although states primarily follow either the solar or lunar calendar, the lunar calendar is used nationwide for religious and social events.
• Indian calendaring can be considered Luni-solar in nature.

Conclusion

• The lecture introduces the basic concepts of Indian calendaring based on sidereal periods and the division of the zodiac.
• Further details and complexities of these calendaring systems will be explored in subsequent lectures.