Jyotihshastra: Astral and Mathematical Literature c4.s6.3

c4.s6.3

Besides the simple śaṅku vertical to the plane of the horizon, Varāhamihira (PS 14)²⁷³ describes a hemispherical sun dial, a perforated ring, and a perforated sphere (in each of the last two instruments perforations 180° apart serve as a diopter). Other instruments mentioned in the siddhāntas are basically illustrative, or are elaborate toys; illustrative are the rotating wooden model of the celestial sphere mentioned by Āryabhaṭa (A. Gola 22–23) or the three-dimensional scale models of the Sines of the planets’ azimuths and altitudes described also by the same astronomer,²⁷⁴ while his clepsydras in fanciful shapes are examples of toys.²⁷⁵ Many later authors of siddhāntas describe these or similar instruments, sometimes in the middle of the text (e.g., MB 3, 56–50), but more often in separate chapters on yantras (e.g., BSS 22; ŚDV II 8; SŚŚ 19; and SŚB II 11). The most significant new instrument introduced in these texts composed before the introduction of the astrolabe into India seems to be the phalaka or board of Bhāskara (SŚB II, 16–27), which is basically a dial with a gnomon suspended vertically in the plane of the Sun’s altitude circle.