Samrat Yantra to tell time again!
Sadly, all the instruments built at the Jantar Mantar Observatory in Delhi, have been lying unused for most part of the 300 years since they have been built. While the other instruments at the Delhi Observatory only need some surface work and markings to be redone on the instruments to make them work again, the Samrat Yantra at the Delhi Observatory has been considered to be unusable in its present condition in all the existing literature on the Observatory.
A view of the Samrat Yantra from the west
The Samrat Yantra at the Delhi Jantar Mantar Observatory, has a unique history. The major change to its structure happened during the renovation of the Delhi Observatory in 1910, just prior to the coronation of King George V. At that time, some of the excavated pit around the central gnomon of the instrument was filled up, as the area had become a swamp. This resulted in the loss of a segment of the quadrant of the instrument on either side of the central gnomon. On account of these missing segments of the quadrants, all the existing literature treats the Samrat Yantra as an instrument that is no longer usable.
The arrow in the photograph above, indicates temporary calibration markings that were made in March 2005, on the horizontal platform near the gnomon of the Samrat Yantra.
Near the central gnomon of the Samrat Yantra, a horizontal cemented platform is present that seems to be a continuation of the quadrant. This platform seems to indicate that the renovation work of 1910 that resulted in the destruction of segments of the quadrant, envisaged a mixed usage of the Samrat Yantra. The instrument can be used as an equinoctial sundial, using the original calibration of Jai Singh's Astronomers on the intact segments of the Samrat Yantra and a calibration analogous to a European sundial on the horizontal platform where the quadrants are missing.
Such a calibration, if successful, will mean a revival of the Samrat Yantra, for daily usage as a sundial. This is what was attempted once in 2005 and being done more rigorously in 2006, by volunteers from the Nehru Planetarium, New Delhi, S.P.A.C.E., and Amateur Astronomers Association, Delhi (voluntary groups doing very good work in Astronomy education). This calibration (with chalk markings) was worked on, rigorously, for about 20 days, just prior to the 2006 September Equinox. It was planned to be tested with public observations on the Equinox day. However, two days of rain washed away all the markings and it is now being planned that the work will be redone around the winter solstice.
It is not very easy to figure out the method to implement a rigorous new calibration scheme for the Samrat Yantra in its present stage. The masonry around the base of the gnomon and the point where the original quadrant meets the horizontal platform is so irregular that an exact determination of the dimensions of these two segments of the instrument is not easily determined. What was tried out therefore, was an observational calibration of the instrument.
With a calibrated sundial, one would look at the sundial time and convert it into the civil time, incorporating the corrections for longitude difference of the location from the meridian corresponding to the civil time being used as well as corrections for the Equation of Time. To make observational calibrations, this process was reversed.
A calibration marking made on any given day, was tested out repeatedly on subsequent days, using the appropriate equation of time for that day. In some cases, accuracy was achieved iteratively, while many markings made for the first time, did turn out to be accurate to 1-2 s at the first attempt. Yes, this is the kind of accuracy possible on account of the immense dimensions of the instrument.
The most arduous of work was put in by Anurag Garg and Dayal Singh of the Nehru Planetarium, for the calibration of the horizontal segments near the gnomon. Vikrant Narang of S.P.A.C.E. and Balachander and R.K. Chikara of the Nehru Planetarium came a close second in this work. The markings were made for every minute and tested out repeatedly. A burst of enthusiasm was then put in by Balachander, Chikara, Dayal Singh and Sneh Kesari on the 21st of September to extend these 1 minute markings on the entire curved segment of the original quadrant. Sneh Kesari, Sagnik Chakravarty, Vidushi Bhatia and Pritpal Kaur lent a hand on some days. Ajay Talwar put in his remarkable expertise of imaging anything to do with Astronomy, lent a hand in photographing some of the results. All in all, this was an amazing amount of work done under a hot sun.
Everything, almost everything, was wiped out by two days of rain, before it could be publicly demonstrated. A few photographs with a clock placed near the markings to check the accuracies do exist to console all of us :-)
The public program function to inaugurate the observations was cancelled. However, voluteers from S.P.A.C.E. and Amateur Astronomers Association, Delhi, were present with renewed enthusiasm to conduct observational activities for the visiting public and students as well explain to them about the new calibration process.
The process of observational calibration of the Samrat Yantra will be continued and demonstrated again during the winter solstice 2006! We are all looking forward to that.
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