Bharatiya Jyotihshastra (History of Indian Astronomy), translated by R. V. Vaidya v2.c12.s5.71.3

v2.c12.s5.71.3

Jaya Simha found that his ideas about the correctness of results could not be realized by brass instruments, because the instruments were small, not convenient for showing minutes of arc, their axes shift their places and get worn out ; the centres of circular plates also shift their places and the planes of instruments get twisted. He thought these to be the reasons why the calculations of Hipparchus and Ptolemy did not tally with observed results. He, therefore, erected the Jaya Prakāś, the Rāma, and the Samrāt instruments which were perfectly stable and built in mortar and stone, whose semi-diameters were 18 cubits, and one grain (yava) in the circumference of which would represent 1 minute of arc. These were constructed and erected with due consideration of geometrical theory, the meridian, and latitude of the place and with careful measurements. They were so designed that it wold be possible to repair the defects caused by the sinking of circular planes, wearing out of axes, shifing of the central points, and irregular spacing of minute divisions. An observatory of this type was built at Delhi. Corrections to be applied to mean motions of planets, which never agreed with observation, were finally determined on the basis of observations taken with these instruments. In order to test the correctness of results of observations taken at the Delhi observatory, he erected similar observatories at Sawai, Jaipur, Mathura, Vāranasī and Ujjayinī.