A comparison is made between coordinates for 35 stars listed in traditional Indian astronomical texts (jyotisa sastras) and the coordinates of corresponding stars listed in modern tables. I find that the error vectors pointing from the modern star positions to the corresponding jyotisa star positions are strongly correlated with the reversed proper motion vectors of the stars. Once precession is taken into account, the modern star positions show a tendency to move towards the jyotisa star positions as we go back in time.

To evaluate this, I first consider the null hypothesis, which says that we should not expect to find a significant relationship between errors in jyotisa star coordinates and proper motions of stars. I give statistical arguments showing that this hypothesis is not correct.

If there is a significant relationship between proper motions and jyotisa star coordinates, then the simplest explanation for this is that the jyotisa star coordinates were measured in the distant past. As time passed, the stars slowly moved from their positions and thereby generated error vectors pointing back along their paths. Given this hypothesis, it is possible to calculate the time of measurement of the jyotisa star coordinates. I find that these coordinates divide into a group 25,000–55,000 years old and a group less than 5,000 years old. There is also a group that cannot be clearly dated, and there is evidence suggesting that the stars in this group may not be correctly identified.  

Additional Notes:

Thompson's 1995 Vita references his presentation as taking place on January 10, 1994 at the Birla Science Center International Symposium of Ancient Indian Chronology. In an in memoriam written in 2008, Rasananda Das offered the following recollection: "In the mid-nineties [Thompson] was invited by the director of the Birla Science Institute in Hyderabad to chair one of the sessions of a conference on 'India Chronology.' Meeting him in the temple I became his research assistant, discovering and collecting the writings of Pt. Kota Venkatachelam, on the basis of which he wrote an article on Indian history according to its own sources for Back to Godhead magazine."

The founding Director of B. M. Birla Science Center in Hyderbad, Dr. B. G. Sidharth, also presented a paper at the conference with the title, "Astronomy, Symbolism, and Ancient Indian Chronology: A Date for the Ramayana," as cited in his book, The Celestial Key to the Vedas (1999), p. 11.