ARTICLE
A set of high-scale observatories located in India, from the XVIII century.
"Jantar" comes from the Sanskrit word yantra and means "instrument", Mantar comes from mantra and means "formula", and both words literally mean "instrument to calculate". It's the name of three of a group of five observatories built by order of prince Jai Singh II between 1724 and 1738, at the end of the Moghul Empire period.
The instruments were built at high-scale and utilized to compare observations and time measurements, which allowed to predict eclipses and other phenomena with great accuracy and only 2 secs of difference! They are located in the N and NW areas of the country: in New Delhi (the ancient main city of the Moghul Empire), Mathurā (already disappeared, the legendary city of Krishna), other two smaller cities in Varanasi (ancient learning centre) and Ujjain (the ancient capital city of Malwa province), and the biggest one in Jaipur (founded in 1726, the capital city of Jai Singh's empire).
The observatories are aligned to the Earth's polar coordinates in such a way that the shadows projected by some of the instruments allow measuring the positions of celestial objects. The instruments are fixated on the ground and built with wood, lime, stone and metals although they are not styled in the expected ways of the usual Indian architecture. Besides, each one of them has its own calibration system (height or ecliptic references), and some of them even allow watchers to choose the reference to use! To understand better the way they work, the observatories have to be visited in daylight time (to see shadows) and have to be considered as groups of instruments providing calculations to be complemented by those of the other ones.
- Great Samrat Yantra
- Great Jai Prakash Yantras
- Rashi Valaya Yantras
- Great Rama Yantras
- Digamsa Yantra
- Kapala Yantras
- Nadivalaya Uttar Yantra
- Dakshino Bhitti Yantra
- Unnatansha Yantra
- Great Astrolabe
I. Great Samrat Yantra
It's the world's largest triangle-shaped sundial, with a 74.1 ft hypotenuse parallel to the Earth's axis, and a gnomon pointing to the North pole.
A 49.2 ft quadrant lies at both sides of the triangle, and the hypotenuse's shadow falls upon its perimeter. The shadow moves 13.12 ft each hour (or 2.36"/min) and it may be read every 6 hs, 15', 1', 6'' and 2''. The instrument was also used to predict equinoxes.
From the top of the gnomon, eclipses and the monsoon season were predicted, too. There's also a Small Samrat Yantra building, one-third the size of the greater one, located at the North boundary of the observatory, next to another instrument specially related to annual seasons (Nadivalaya Uttar Yantra). The Small Samrat is 22.6 ft high, and the smallest division of the scale in the quadrants allows measuring a 20'' timelapse.
The following video is a 20' timelapse for seeing better the way the shadow moves across the quadrants' perimeter:
index
II. Great Jai Prakash Yantra
(aereal and underground views)
Two big semi-spheres partially emerge from the ground, 16.4 ft each one and with one of the two reference systems marked on the surface.
There're gaps for a viewer to walk between them and align the eye right on the surface where the object of interest is marked up. If both surfaces were joined, a continuous sphere would appear (where one semi-sphere has a gap, the other one has a solid area).
As time passes by, a viewer locates objects in the marked bands on the surfaces (each band is 1 hour of Earth's rotation). When the position of the object is no longer aligned to the surface (when is beyond the limit of the area), a viewer just has to walk to the other semi-sphere to continue observing the object's pathway during the next hour.
Two wires cross each semi-sphere from above, oriented according to the 4 cardinal orientations and intersected in the centre of the instruments. A small metal ring hangs in the intersection and indicates the zenith by casting a shadow, which allows locating the Sun's position. Other concentric circles around it represent declinations.
index
III. Rashi Valaya Yantras
Rashi Valaya is a group of 12 structures representing the constellations of the Zodiac. They're designed according to the Great Samrat Yantra's structure but their measurements continue those of the Jai Prakash to calculate the objects' longitude and latitude: when a sign of the Zodiac is crossing the meridian, the plane of the quadrants remains parallel to the plane of the ecliptic, and the gnomon points to the Pole.
index
IV. Great Rama Yantra
They're two drum-shaped cylindrical buildings, with elevated surfaces and a central pillar.
Like those of the Jai Prakash, each building holds within serialized divisions for a viewer to move between them (gaps) and, if both buildings were joined, they would complement each other by forming a single drum.
The floor and the inner surface of the walls are marked by scales of angles. By drawing a line connecting a celestial object to the top of the central pillar, the lower extreme of that line would point to a scale marked on the floor (or on the building's wall), which provides the object's altitude.
There are two other Rama Yantras, although smaller ones, on the Western side of the Rashi Valaya.
index
V. Digamsa Yantra
Located between the two buildings of the Great Rama Yantra, it's an instrument to measure altitudes. For that purpose, a thread is bounded to the central pillar and extended to the external wall, with a stone creating tension and a vertical plane crossing the object of interest. A mark on the inner and external rings provides the angle of declination referenced to the North Pole.
indexVI. Kapala
Other two Jai Prakash Yantras are located on the Western side of the previous ones. They're smaller than those seen above and, in between them, two big circular irons inclined according to the Earth's axis include parallel axes to the Equatorian plane, which allows measuring the Sun's position and declinations.
Like the Great Jai Prakash's instruments, a metal ring in the Northern iron (on the right side of the image) hanging on two crossed wires casts shadows although it contains inscriptions of the two measuring systems. It is considered that the Kapalas forerunned the Jai Prakash, and the latter ones would be a later display of this instrument. The Southern iron is not meant for observations but for transforming the coordinates from one of the systems into those of the other one.
index
VII. Nadivalaya Uttar Yantra
(views from above and one side)
They are two sundials to calculate equinoxes. For that purpose, each circular panel is parallel to the plane of the equator, and a thin stick fixed in the centre (parallel to Earth's axis) casts a shadow on the sundial's surface.
One of the panels faces North and is utilized in Summer time, and the other one faces South and is used in Winter.
index
VIII. Dakshino Bhitti Yantra
In the North area of the Great Samrat Yantra, in the limits of the observatory, there's another instrument oriented to both East and West.
The East side (first image) includes two quadrants of 19.6 ft radius, and the West side (second image) is a semi-circle of a little bit smaller radius. A small central stick allows calculating declinations, with variations of degrees and minutes.
Dakshino Bhitti Yantra
index
IX. Unnatansha Yantra
To the West of the Dakshino Bhitti Yantra, a big ring hangs from a mounting, a 16.4 ft diameter metal instrument that turns around a vertical axis.
It's utilized along with a tube to calculate the objects' altitude and longitude by placing a "sight" inside of the central hole, at any time of the day or night.
index
X. The Great Astrolabe
Built from a single piece of copper, weighing more than 880 lb and of 7.97 x 6.92 ft in size, it's the world's biggest astrolabe of its kind!
It's located at the North side of the observatory (in the image: Unnatansha Yantra is behind the pillar, and Dakshino Bhitti is visualized in the right background).
The Hindu government declared the observatory in Jaipur a monument of national interest in 1968 but the instruments have been exposed to tropical weather, vandalism and war, and have been frequently restored. During those restorations, marble has been inserted in the markers on surfaces and the Hindu's measurement system has been replaced by the Western one (muhûrta = 48', ghati = 24', kâla = 48'', pala = 24''...).
You may find more references in the sources below.
indexSources: The astronomical observatories of Jai Singh, Jantar Mantar Entry Fees, UNESCO, Jaipur Jantar Mantar: worlds largest sundial por Rohit Gurjar, Jaipur's Jantar Mantar de Madhuri Katti, India 3. Jaipur. Observatorio medieval Jantar Mantar, The Jantar Mantar of Jaipur, Jantar Mantar Observatory.,Calendario hindú.
Photos.: Anupamg, CC BY-SA 3.0 and Narivalaya wiki: G41rn8, CC BY-SA 4.0 via Wikimedia Commons.
Comments
Join and leave a message. I always answer personally, and as soon as possible.