Page 26 - Guidelines for Training/ Orientation of Faculty on IKS

Guidelines for Training/ Orientation of Faculty on IKS

these elements in a Pañcāṅga. Explain how to compute the average period of a lunar
month; Bring out the need for the introduction of an adhikamāsa in the calendrical
system. Outline the broad categories into which different calendars that are followed can
be put into— namely solar, lunar and luni-solar.
7. Key concepts pertaining to planetary computations
 The revolution numbers of various planets, nodes, apogees, etc.; The count of the number
of civil days, adhikamāsas, etc. in a mahāyuga. Introduce the concept of Ahargaṇa, and
its significance; The basis for choice of epoch. Calculation of Ahargaṇa; Illustration with
a few numerical examples choosing contemporary dates – using siddhāntic text (to begin
with). Explain the computation of mean motion of planets, and how its computation
along with the Ahargaṇa can help in finding the mean position of planets.
8. Computation of the true longitudes of planets
 Provide an overview of the steps involved in the computation of the true longitudes.
Explain manda-saṃskāra in detail using epicyclic model and eccentric model. Outline
the nature of the resultant orbit, etc, and explain how this correction takes into account
the eccentric nature of the planetary orbit. Emphasise and make the students appreciate
the simplification achieved in computation by the ‘constraint’ r/R = r0/R. Explain śīghra-
saṃskāra in detail; Point out how this correction boils down to the transformation of the
heliocentric coordinates to geocentric. Also indicate how this simple model takes care of
the retrograde motion of the planets. Bring out the distinction between the inner and outer
planets.
9. Precession of equinoxes – sāyana and nirayaṇa longitude
 Introduce the concept of precession of equinoxes. Explain solsticial and equinoctial
points, and connect them to the concept of uttarāyaṇa and dakṣiṇāyana in the Indian
calendrical system. Derive the formula for finding the declination of the sun on any day
at any time, and also illustrate it with examples. Also highlight how crucial its accurate
computation is for the computation of various other quantities precisely — including the
problem of finding the direction and the latitude of the place — even if we choose to do
them by experimental methods.
10. Finding the cardinal directions and the latitude of a place
 Introduce śaṅku (the gnomon), and explain how it has to be prepared as described in the
texts. Describe the experimental set up that has to be made meticulously for conducting
experiments with śaṅku and doing shadow measurements. Explain how with a very
simple experiment the directions at a given place can be easily and precisely determined.
Also point out that this experimental method is very old—described even in the
Śulbasūtras. Also outline the theoretical basis for the formula that has been given for
correcting the points marked in connection with determination of the direction using
śaṅku. Bring out the versatility of this simple device śaṅku in determining a variety of
physical quantities of interest including the latitude of the place. Explain the concept of
parallax in general, and how it introduces an error – that is unavoidable in conducting
this experiment for determining the latitude of the place. Outline the corrections that
have been prescribed in the text that would take into account the above error, as well as
the fact that sun is not a point source of light.
11. Determination of the variation of the duration of the day at a given location
 Introduce the 6’o clock circle and its significance. Derive the formula for the hour angle
at sunset, and explain how the latitude and the declination of the sun play a role in it.

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