Calculating Tithis in the Hindu Calendar - Petrix108's Query

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SUMMARY

The discussion focuses on calculating tithis in the Hindu Calendar, defined as a lunar day marked by a 12-degree difference between the Sun and the Moon. Petrix108 seeks a mathematical formula, potentially trigonometric, to determine the exact time a tithi begins and ends based on the angular relationship between the two celestial bodies. The conversation highlights the importance of the hour angle or right ascension in these calculations. An average duration of 23 hours, 37 minutes, and 28.1 seconds is suggested for practical purposes.

PREREQUISITES
  • Understanding of lunar phases and their significance in the Hindu Calendar
  • Basic knowledge of trigonometry and angular measurements
  • Familiarity with astronomical concepts such as hour angle and right ascension
  • Experience with mathematical modeling and calculations
NEXT STEPS
  • Research the mathematical principles behind lunar phase calculations
  • Learn about the hour angle and its application in celestial mechanics
  • Explore trigonometric formulas relevant to angular displacement
  • Investigate existing algorithms for calculating tithis in various lunar calendars
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Astronomers, mathematicians, and enthusiasts of the Hindu Calendar seeking to understand the precise calculations of lunar days and their applications in cultural contexts.

petrix108
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Dear Physics/Astronomy Forum Folks:

I have been recently reading, studying about an interesting feature of the Hindu Calendar, called the tithi, which is basically a lunar day, or a difference of 12 degrees between the Sun and the Moon. Now the angular speed of the Moon in relation to the Sun, which determine the cycle of lunar phases, is not constant or even linear. My question is: does anyone know how to find the exact mathematical relationship (a trigonometric formula maybe?) using which one could calculate the exact time within a day, when a certain tithi starts and ends. I've read on some other forum that it's got to do with the difference between the hour angle or right ascension of the Moon and the Sun. So given, for instance the exact time and day of the New moon or the Full Moon, how does one calculate when the exact time is that 12 degrees have passed between Sun and Moon? What is the formula for calculating tithis?

Thank you for your help,
Ys, Petrix108
 
Astronomy news on Phys.org
twofish-quant said:
Google is your friend...

For most purposes, I'm guessing an average would work almost as well: 23 hours, 37 minutes, 28.1 seconds.
 

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