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Updated: May 6, 2025
Bradley in 1721 actually observed Mars with a telescope "moved by a machine that made it keep pace with the stars;" and Von Zach relates that he had once followed Sirius for twelve hours with a "heliostat" of Ramsden's construction. But these eighteenth-century attempts were of no practical effect.
Outside of these, the professor had established his heliostat, and then gradually, by the aid of drapery, he narrowed down the entrance of light to a little aperture where a single silver bar entered and pierced the darkness like a spear. Then this was closed by the insertion of his microscope, and, leaving his apparatus in the hands of an assistant, he felt his way back to his old position.
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