Galileo and his Galileo and his TelescopeTelescope

Practical Optics and Practical Optics and CosmologyCosmology

Albert Van HeldenRice University

University of Utrecht

The telescope was invented by children playing with

lenses?

. . . . .

Hans Lipperhey’s

patent applicationOktober 1608

Jacob Metius of Alkmaar

And then there was also

Sacharias Jansen

Giovanni Battista della Porta

1535-1615

Concave lenticulars show things clearer but smaller. Convex lenticulars show things larger but fuzzy.

If you know how to put the two together, you will be able to help near-sighted as well as far-sighted people. Magia Naturalis, 1589

Gio. Battista Della Porta to Federico Cesi28 augustus 1609

“e una coglionaria et e preso dal mio libro 9 De refractione”

Italian Spyglass

First half of the 17th centurylength 21 cm, magnification 4×

courtesy of R. Willach

French telescope, ca. 1620

length 63 cm, magnification 14×

courtesy of R. Willach

1610 1616

Il saggiatore, 1623