Galileo Telescope

In 1609 Galileo Galilei heard of a Dutch invention that magnified distant objects. Galileo made several of his own low power ( 3x, and 8x ) “spyglasses” and a few months later a 21 power version which allowed him to see mountains and craters on the Moon, the satellites of Jupiter, and countless stars that could not be seen with the naked eye. He published the accounts of his observations in March of 1610 (The Starry Messenger).

Two of Galileo's telescopes, including the one he is believed to have used in his 1609/1610 discoveries, are on display in the “Institute and Museum of the History of Science” in Florence Italy. That telescope has a concave objective lens with a diameter of 37mm and a FL of 980mm. The eye piece lens is missing but Galileo's notes indicate it was a convex or negative lens with a FL of -50mm and a diameter of 22mm. The negative eye lens is set inside the focal length of the positive objective lens. This gives an upright image but with a very small field of view. When viewing the Moon, only about 25 percent of it is visible.

Johannes Kepler suggested using a positive (convex) eye lens beyond the focal point of the objective lens. This creates an inverted image in a somewhat longer telescope but with a much larger field of view.

Galileo made his tubes and lens cells or holders with two or more layers of thin wood strips held by a resin glue which fills the gaps eliminating the need to chamfer the edges of the strips. Galileo likely used an animal based glue, but I had good results using ordinary wood glue.

The original scope is covered with leather. Mine is covered with vinyl.