Jantar Mantar Observatory at Delhi
new Calibration work on the Samrat Yantra
Jantar Mantar - were a series of masonry observatories built by Raja Swai
Jaisingh of Rajasthan during the early 18th century. He had been perturbed by
finding
that the calculated celestial elements for the Sun, Moon and Planets - predicted
positions in the sky at different times - as calculated using classical Indian
Astronomical concepts - seemed to disagree with observations.
The one underlying reason for this had been the fact that for more than a
thousand years - the calculating algorithms for Celestial object positions - had
not been corrected for the precession of Earth's axis of rotation.
This effect was observed as far back as the Vedic times - and termed Ayanamasa.
Whenever calculated elements strayed far from predicted ones, due to precession,
ad-hoc corrections used to be applied to these - termed Bija corrections - so
that the calculations would agree with observations.
However, these corrections were never systematised and many classical treatise
did not mention these. And increasingly Indian Astronomy had been moving away
from observational verifications of Astronomical calculations - they were being
used more for astrological purposes - with obscure planetary formations being
talked about that ordinary people could not verify.
Anyway, this was the history behind the perplexities that both Swai Jaisingh
faced in early 18th century and Samanta Chandrasekhar encountered it again late
in the 19th century. I think, many non standard uncorrected panchangs exist even
to this date. Both Jai Singh and Samanta Chandrasekhar felt that what was needed
was corrections to be applied to the existing methods of calculations - with
precise observations. For these precise observations, Jaisingh's choice was
giant masonry instruments and those of Pathani Samanta (who, unlike Jai Singh,
lacked any financial backing) was to construct simple hand made instruments and
make meticulous observations with these.
Jai Singh had the Samarkand Observatory of Ulugh Begh as his inspiration - he
learned from Indian and Persian sources and innovated modifications on several
instruments from his reading.
The Delhi Observatory consisted of four main instruments each of which had other subsidiary functionalities inbuilt. The first two listed here having the main functionality of time measurements with some other functions, built in. The latter two instruments were meant, mainly for celestial co-ordinate measurements for the Sun, Moon, planets and stars.
Samrat Yantra - An equinoctial Sun dial - the largest and the most imposing structure at the Observatory.
Misra Yantra - A mixed instrument which incorporates many interesting functions.
Jayaprakas - The 'Crest Jewel' of instruments consisting of two complimentary concave hemispheres, reflecting the dome of the sky.
Ram Yantra - Two imposing circular complementary buildings, designed for very easy determination of local celestial co-ordinates.
This page will be updated with more information about Jai Singh's observations with these instruments. Please check back at a later date.