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well to enable Kepler to discover the true
theory of the solar system. But telescopic
sights and clocks were required for proving
some of Newton’s theories of planetary per-
turbations. Picard’s observations at Paris
from 1667 onwards seem to embody the first
use of the telescope as a pointer. He was
also the first to introduce the use of Huyghens’s
clocks for observing the right ascension of
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