The design of the first optical
telescopes in the 1570's was a simple design. There was one concave
and one biconvex lens fitted inside a tube. The lenses bend the light
as it passed through the glass and made the image 3 to 4 times larger.
Galileo in 1609 made a telescope with 20-power refracting telescope.
It created quite an international commotion because he discovered the
valleys and mountains of the moon and discovered 4 moons of Jupiter.
This design could make an image larger, but the tube had to be larger
and the lenses needed to be larger. Astronomers were creating monster telescopes up
to 150 feet long with a lens of 1 meter (3.28 ft). That was just too