Page 28 - Guidelines for Training/ Orientation of Faculty on IKS
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Guidelines for Training/ Orientation of Faculty on IKS
Course 7: Introduction to Indian Astronomy
SEMESTER I
1. Preliminaries
Sky viewed as the inside of a hemisphere. Cardinal directions, zenith, horizon, pole star
at any location. Daily motion of celestial objects (Sun, Moon, planets, stars) and diurnal
circles. Motion in the stellar background. Ecliptic. Basic time units: Day, Month and
Year. Celestial coordinates and elementary spherical trigonometry. Cosine and Sine
formulae. Horizontal (z,A), Equatorial (δ, α and H), and Ecliptic (λ, β) systems.
cos z = sin φ sin δ + cos φ cosδ cos H, and other relations. Planetary positions.
2. Developments from the Vedic period up to the Siddhāntic period
Vedic Astronomy: Astronomical concepts in Vedic literature regarding Sun, Moon, Stars,
Earth. Months, seasons, year. 27 nakṣatras. Ecliptic and ayana. Planets, Comets etc.
Pole star in an earlier era. Nakṣatra division of the ecliptic and motion of the Sun along it
in Vedāṅga Jyotiṣa (VJ) and other texts. VJ calendar. VJ computations. Duration of a
day. Better value for an year in Vedic literature.
Siddhāntic astronomy: Earlier Siddhāntas and Pañcasiddhāntikā. Introduction of
trigonometry, Indian jyā–astronomy. Āryabhaṭīya . Mahāyuga. (Kalpa etc., and also
smaller units of time can be introduced at this stage). Revolution numbers of planets.
Ahargaṇa and Mean longitudes, Examples. Obtaining the true longitudes by applying
corrections to mean longitudes.
Epicycle models: Manda correction (Equation of centre) in detail. Its significance.
Latitude of Moon.
Śīghra correction to planets and its significance: Essential features only with the aid of
diagrams and final formulae. Latitudes of planets.
Precession of equinoxes— Nirayana and Sāyana longitudes.
Nature and organisation of texts. Sūtra (algorithmic) format. Siddhānta, Tantra,
Karaṇa and Vākya texts. Sāraṇis or Tables.
3. Indian Calendar
Pañcāṅga. Adhikamāsas. Solar and Luni-Solar systems.
4. Solar and Lunar Eclipses
Angular diameters of the Sun, Moon and Earth’s shadow. Possibility of eclipses. Finding
the middle of an eclipse by iteration. Amount of obscuration at any time.
5. Tripraśna Topics (Diurnal problems)
Description of the celestial spheres and various circles. Similarity to modern description.
Determination of the East-West directions. Derivation of the expression for the
declination in terms of the longitude. Shadow of a gnomon. Equinoctial day when the
locus of the tip of the shadow is a straight line. Finding the latitude. Mid-day shadow.
Finding the declination. Relation between the time and the shadow at an arbitrary instant
(no derivation).
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