Abstract
IN the beginning of the year 1608, that is, 315 years ago, or about ten generations, telescopes did not exist. The main work of astronomers before the year 1608 was, therefore, concentrated upon observing and recording the positions of the heavenly bodies from day to day and from year to year. The early (1587) instruments for observations of position took the form of graduated quadrants mounted in a vertical plane capable of rotation about the centre of a horizontal divided circle. The direction of a heavenly body could be indicated only by pointing at it; so every quadrant was furnished with a pointer pivoted at the centre of the quadrant. The adjustments of the instruments were made by using a plumb line for the determination of the vertical, and a level for placing the azimuth circle horizontal.
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LOCKYER, W. The Growth of the Telescope. Nature 112, 284–288 (1923). https://doi.org/10.1038/112284a0
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DOI: https://doi.org/10.1038/112284a0