Mahādevī-sāriṇī: A unique table providing true longitudes of planets

Abstract

Finding the true longitudes of planets had always been a challenge for early astronomers. As keen observers, they noted the small drift of the planets from the calculated positions and rectified them from time to time. Such efforts are traceable in many texts. One such table is the Mahādevī-sāriṇī of the fourteenth century. The paper discusses the methodology of reading the true positions directly from the table using the mean positions and compares it with some later manuals of the seventeenth century. An example of the application of the conjunction of December 21, 2020, reveals that these tables for true longitudes are relevant even today. The efforts to improve accuracies achievable from naked-eye observations can be traced.