1761 and 1769 were important years for astronomy, scientific knowledge, and world exploration.

[a425couple]

1761 and 1769 were important years for astronomy, scientific knowledge,
and world exploration. Mankind's scientific work in astronomy,
geography, and mathematics had progressed to where they could predict
that Venus would transit between the Sun and the Earth, and they
knew if the could accurately time that passage, they could finally
calculate the size of, and distance to the Sun.

But those transits only happen about twice a century, and they
will not wait until mankind is ready. So, hurry and explore!

This is a fairly interesting and informative book
about that effort and exploration.

https://www.amazon.com/Day-World-Discovered-Sun-Extraordinary/dp/1522605320

The Day the World Discovered the Sun,
by Mark Anderson (Author)
An extraordinary story of scientific adventure and the race
to track the transit of Venus.

The above cite has a "look inside" feature, so anyone can
for free read the first 12 pages.

"On June 3, 1769, the planet Venus briefly passed across the face of the
sun in a cosmic alignment that occurs twice per century. Anticipation of
the rare celestial event sparked a worldwide competition among aspiring
global superpowers, each sending their own scientific expeditions to
far-flung destinations to time the planet's trek. These pioneers used
the Venus Transit" to discover the physical dimensions of the solar
system and refine the methods of discovering longitude at sea. In this
fast-paced narrative, Mark Anderson reveals the stories of three Venus
Transit voyages—to the heart of the Arctic, the New World, and the
Pacific—that risked every mortal peril of a candlelit age. With time
running out, each expedition struggles to reach its destination a quest
that races to an unforgettable climax on a momentous summer day when the
universe suddenly became much larger than anyone had dared to imagine.

The Day the World Discovered the Sun tells an epic story of the enduring
human desire to understand our place in the universe.

see also
https://en.wikipedia.org/wiki/James_Cook
Cook's first (of 3) world wide voyages was to time Venus Transit.
In this, and his other voyages he greatly expanded man's
knowledge of world geography.

see also
https://en.wikipedia.org/wiki/Transit_of_Venus
"Maximilian Hell published the results of his expedition in 1770,
in Copenhagen.[48] Based on the results of his own expedition,
and of Wales and Cook, in 1772 he presented another calculation
of the astronomical unit: 151.7 million kilometers."