ABSTRACT
Most of the notable astronomical instruments of the period were manufactured in London or in Paris. When the telescope was first employed in astronomy, early in the seventeenth century, it was regarded simply as a means of producing magnified images of interesting celestial objects. In accordance with the twofold function which the telescope had come to fulfil in the seventeenth century, the astronomical instruments of the eighteenth century fall into two main classes. Those primarily intended for making precise measurements of angular magnitude on the large scale or for the determination of time, and those primarily designed for prolonged examination of the features of celestial objects and for their micrometric measurement. Edmund Halley planned the erection of a similar instrument to cover the northern quadrant. A tendency to break away from the cumbrous instruments of essentially pre-telescopic design had, however, begun in the closing years of the seventeenth century with the invention of the transit instrument by Olaus Romer, about 1690.
