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rants, sextants, and large celestial globes.
With these he measured the positions of
stars, or the distance of a comet from sev-
eral known stars. He has left us full de-
scriptions of them, illustrated by excellent
engravings. Previous to his time such in-
struments were made of wood. Tycho al-
ways used metal. He paid the greatest at-
tention to the stability of mounting, to the
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