Reduction to observation

  • K. Ramasubramanian
  • M.S. Sriram
Part of the Sources and Studies in the History of Mathematics and Physical Sciences book series (SHMP)


The latitude of the Moon, multiplied by the equinoctial shadow and divided by 12, has to be subtracted from the true longitude of the Moon if the latitude is north at sunrise. At sunset it has to be added.

If the declination is south, then the application is reversed and there is no correction when the Moon is at the centre [zenith]. The product of latitude in minutes and the declination of the point whose longitude is 90 degrees plus that of the planet in degrees, [which is] in seconds, is added to or subtracted from the longitude of the planet depending upon whether the declination and the latitude are in different hemispheres or in the same hemisphere.


Earth Orbit Planetary Orbit Spherical Triangle Retrograde Motion Interior Planet 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. [GYB 2008]
    Gaṇita-yukti-bhāṣā of Jyeṣṭhadeva, ed. and tr. by K. V. Sarma with Explanatory Notes by K. Ramasubramanian, M. D. Srinivas and M. S. Sriram, Hindustan Book Agency, New Delhi 2008 (repr. Springer 2009).Google Scholar
  2. {SSR 2000}.
    Siddhāntaśiromaṇi of Bhāskarācārya-II, Grahagaṇitādhyāya tr. by D. Arkasomayaji, Rastriya Sanskrit Vidyapeetha, Tirupati 2000.Google Scholar
  3. 2.
    S. Balachandra Rao, Indian Astronomy: An Introduction, Hyderabad 2000.Google Scholar
  4. 5.
    Dennis Duke, The Earth in India: the mathematical basis of ancient Indian planetary models, Arch. Hist. Exact. Sci., 59, 563–576, 2005.MathSciNetMATHCrossRefGoogle Scholar

Copyright information

© Hindustan Book Agency 2011

Authors and Affiliations

  1. 1.Department of Humanities and Social Sciences, IIT BombayCell for Indian Science and Technology in SanskritPowaiIndia
  2. 2.Department of Theoretical PhysicsUniversity of MadrasChennaiIndia

Personalised recommendations