The most fascinating monuments in India for me are the Jantar Mantar's. Literally the word Jantar Mantar means "calculating instrument", but the term also has a mystical feeling of something very unique or even magical. Unlike other monuments that were built as forts, palaces, universities and religious sites, the Jantar Mantar's are arguably the only ones devoted to pursuit of science. Unlike a university that is largely involved in teaching, these are actual astronomical instruments. It is believe that the instruments were built to have a more accurate calendar that could be used to decide auspicious days for the royalty to undertake important tasks.
The Jantar Mantar's (in five different cities) were built by the Rajput king Sawai Jai Singh II (3 November 1688 – 21 September 1743). Note the link to 3rd November and JA. The biggest of the Jantar Mantar's is located in Jaipur, the capital of Jai Singh II. As fate would have it, i visited this Jantar Mantar recently. It has 19 different instruments built to do fairly different tasks. The pictures are posted on the English wiki. While Jai Singh's contributions are well recorded, his chief astronomer Pandit Jagannatha Samrat is probably not as popular. It is conceivable that Samrat played a very important role in the design and construction of the Jantar Mantar's as it has to be noted that Jai Singh was also involved in conducting the royal duties of ruling and conducting war. Samrat is credited with writing Siddhānta-samrāṭ and Yantra-prakāra which provide useful details about the design, construction and use of astronomical instruments. A more recent general article that provides a comprehensive idea about the Jantar Mantar's is written by N Rathnasree.
In this post we start with the Unnatamsa Yantra. Unnat meaning elevated and Amsa: division or degree of arc put together gives the word "Unnatamsa". The word Yantra meaning machine is added as a suffix to each of instruments. This instrument is used to measure the altitude - the angular height of an object in the sky. It consists of a large graduated brass circle that is hanging from a supporting beam and is pivoted to rotate freely around a vertical axis. A sighting tube is provided at the center of the circle at the intersection of two cross beams in the vertical & horizontal directions. The sighting tube can be moved in the vertical direction to align it towards celestial objects. The pivoting used in the Unnatamsa is analogous to the Alt-Azimuth mounting used in modern telescopes.
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Unnatamsa Yantra |
The altitude of celestial objects can be measured by looking at the graduations on the rim of the brass ring after locating the object using the sighting tube. The graduations on the rim of the circle are able to distinguish upto one tenth of a degree. Larger deviations of 1 degree and 6 degrees are marked with longer graduation marks.
