Astronomical Efforts of Sawai Jai Singh
- A Review

The Telescope

Though Jai Singh's instruments are nontelescopic, he was aware of the telescope and to some extent, of its potential as well. He had bought one at a cost of Rs. 100 for his personal library (Tozis 3). In his Zīj-i Muhammad Shahī, while introducing a chapter, " The visibility of Moon", he states, "These rules are for naked-eye observations only, although the telescope is now being made in the country. The telescope enables one to see bright stars in broad daylight also -- say around the noon hour. It also enables one to see the moon when there is hardly any light in it, or when its face is totally dark and invisible... The planet Saturn (Through a telescope) appears oval in shape, an oval whose lower half is larger than the upper. Around the planet Jupiter there revolve four bright stars. On the face of the Sun there are spots, and the Sun rotates on its axis within a period of one year" (See Zīj Jadīd Muhammad Shāhī, f. 189). He goes on to add, "Since the telescope is not readily available to an average person, we are going to base our rules of computations for the naked eye only" (Zīj Jadīd Muhammad Shāhī, f. 189).

Thus the telescope was indeed available to Jai Singh and his astronomers, and they did use it to some extent at their observatories. In the astronomical endeavors of Jai Singh, it is not the telescope but the "telescopic sight" that is missing. His instruments are not designed to incorporate the telescopic sight. The author believes that the telescopic sight, which had been accepted only decades earlier by the astronomers of Europe, did not reach Jai Singh in time.

Jai Singh's statement regarding the shape of Saturn suggests that the telescopes available to him were of inferior quality. His erroneous statement about the rotational period of the Sun indicates that there was no sustained program of observing in general with the telescope. His lack of interest in telescopic observation, and that of his astronomers as well, is further indicated by the fact that Jagannāth does not include the telescope among the yantras for an observatory (Sharma, R.S. 1967, Yantrādhyāya).

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