Bharatiya Jyotihshastra (History of Indian Astronomy), translated by R. V. Vaidya v2.c12.s5.58

v2.c12.s5.58

DHRUVA-BHRAMA-YANTRA :—PADMANĀBHA, son of Nārmada compiled this work. It has already been pointed out (page 126) that the date of this Padmanābha is about Śaka 1320. The work consists of 31 verses and has a commentary written by the author himself. This instrument known as Dhruvabhrama Yantra is meant to find time and it consists of a rectangular plank of wood, the length of which is double the width, and which has a chink bored in it parallel to the shorter edge; the constellation of Dhruva-matsya (polar fish) is to be observed through the chink. The author does not intend to describe here in the construction of the instrument meant for finding time. The author has described the “ Polar fish ”* in the following words :— “ There is a cluster of 12 stars round the North Pole. It is called the ‘ polar fish ’. It has two bright stars, one of which is regarded as its mouth and the other as its tail. One of these is on one side of the pole at a distance of 3° and the other lies at a distance of 13° on the other side.” The author has described the construction of an instrument by which time can be noted at night by observing the stars situated at the mouth and the tail. A method has been described for finding time by observing other stars at night and even the Sun during the day. Similarly, even the ascendant at any moment is found with the help of this instrument, and it evidently gives the sāyana ascendant. The mean altitudes of junction stars of 28 asterisms at transit as observed in latitude 24° N have been mentioned. It shows that the author may have been the resident of a place whose latitude is 24°.