Page 27 - Guidelines for Training/ Orientation of Faculty on IKS

Guidelines for Training/ Orientation of Faculty on IKS

Explain the concept of cara as outlined in the Indian astronomical texts that captures the
variation in the duration of the day at a given location. Present the formula for
determining the local time using shadow measurements. Also outline how cara plays a
role in determining this local time. Bring out the distinction between this local time and
the standard time that we are generally familiar with and generally keep track of.
12. Lagna and its computation
 Introduce the concept of lagna, and how non-trivial a problem it is to determine it
precisely. Also point out how this is deeply connected with fixing times for various social
and religious functions such as marriage, etc. Bring out the connection between its
computation and the computation of declination, cara etc. that would have been
discussed before. Explain how this can be determined ‘reasonably’ accurately using
interpolation. Also outline more precise formulations that have been given by later
astronomers by introducing the notion of kālalagna.
13. Eclipses and their computation
 Briefly explain the phenomenon of lunar and solar eclipses, and the crucial role played
by the position of the lunar nodes in their computation. Also bring out how difficult it is
to precisely determine the position of the nodes—as they are not physical objects
available for observation. Explain how the latitude of the moon is computed, and then
outline the procedure for the determination of the semi-diameters of the eclipsing and
the eclipsed bodies. Derive the simple formula for determining the duration of eclipses
as well as the obscuration. Also mention that iterative procedures are followed to
improve accuracy. Point out the role of parallax in the determination of solar eclipses.

References:
nd
1. S. N. Sen and K. S. Shukla, History of Astronomy in India, 2 Ed., INSA, Delhi, 2001.
2. S. Balachandra Rao, Indian Astronomy An Introduction, Universities Press, Hyderabad, 2000
3. History of Astronomy: A Handbook, Edited by K. Ramasubramanian, Aniket Sule and
Mayank Vahia, SandHI, IIT Bombay, and T.I.F.R. Mumbai, 2016.
4. B.V. Subbarayappa and K.V. Sarma, Indian Astronomy: A Source Book, Nehru Centre,
Bombay, 1985.
5. Tantrasaṅgraha of Nīlakaṇṭha Somayājī, Translation and Notes, K. Ramasubramanian and M.
S. Sriram, Hindustan Book Agency, New Delhi 2011.

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