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Galilean Telescope

The knowledge and manufacture of lenses were known since the time of the old Greeks (the word optics came from the Greek word ὀπτικά, which means appearance) and later in the old ages with Egyptian scholar Alhazen who made important contributions to the study of optics in general. In Europe, the lenses arrived around 13th century and immediately triggered the invention of the first eyeglasses. However, one important discovery had to wait three centuries later in order to set off a wave of new discoveries in the field of astronomy. The invention was made by Hans Lippershey, the spectacle maker from the Dutch city of Middelburg in Netherlands, who in October 1608 tried to apply for a patent for a tool he described as an aid capable of "seeing faraway things as though nearby". It consisted of a convex and concave lenses in a tube capable of magnifying objects three or four times. For strange reasons, the patent was rejected, but the new instrument immediately attracted attention. Now known as spyglass, the invention ushered in a new era in astronomy and was the foundation of today's refracting telescopes.

Cardboard replica of the original telescope made by Galileo

Only half a year later, in the early summer Galileo Galilei, at the University of Padua near Venice started to build his first telescope based on the one Hans' made. He managed to design and build telescopes with increasingly higher magnifying power for his own use as well as for presents to his patrons. Galileo was a skilled instrument maker, and his telescopes were known for their high quality. Just like initial spyglass from Netherlands, his first telescope was basically a tube containing two lenses but he managed to enhance the power that magnified objects approximately nine times with his first designs.

Even though Galileo perfected the manufacturing of lenses and telescopes - in later years he managed to produce over a hundred telescopes and some of them with magnifications as high as 33 - only two have survived and can be seen in the Museum Galileo (Museo di Storia della Scienza) in Florence. One of the two, especially designed for Cosimo II de' Medici, Grand Duke of Tuscany, with gold-embossed leather, probably had (with initial lenses from the end of 1609) magnification power of around 20. The limiting factor of these early refractors, especially those with higher magnification was their small field of view but still, it allowed Galileo to see that Milky Way is just a multitudes of millions of stars and that the Moon's surface was not smooth and perfect but rough, with mountains and craters whose shadows changed with the position of the Sun. He saw the phases of Venus throughout the year and the most interesting fact that planet Jupiter was accompanied by four tiny satellites which moved around it with distinctive proof that not everything in the heavens revolves around the Earth.

Phases in assembling Galileo's historical telescope

This particular, gold-embossed leather telescope from the Florence museum was the model for the AstroMedia cardboard replica kit I got my hands on last weekend. It was advertised as "with this historically accurate cardboard replica, you can experience first hand the great research achievements of Galileo, which he achieved despite the optical performance of this telescope, which is modest by today's standards". All I could say after two days of carefully pasting pieces of paper one after the other was that I couldn't agree more, especially at the last moment when I pointed it to the one kilometer away sign of the neighboring shopping center and clearly read what it said. I can only imagine where Galileo pointed his first telescope to and what was his initial reaction.

While Galileo did not invent the telescope in the first place, his contribution toward their use in astronomy and science, earned him two phrase coins: Galilean Telescopes, now represents a popular name for a refraction telescope type and Galilean Moons, now referring to the first four of Jupiter's natural satellites.

Jupiter's moons as seen through modest reflecting telescope compared to the view
from a small refracting spyglass similar in size to Galileo's original telescope

Unfortunately, I cannot make any astronomy photos with this replica, after all it is made of cardboard and fixing it on the moving sky is a mission impossible, not to mention it's extremely small field of view, which is perhaps less than a centimeter in apparent terms which would provide only troubles for focusing camera through it. For these reasons, I decided to embed a photo of a Jupiter's moons as seen with a modest reflecting telescope (the one you can see in the background of the first image above). Below you can find a link to the YouTube video of the entire event we created couple of years ago when Jupiter was close to Earth. In the upper right corner of the photo I also included a small view of how Galileo might have seen Jupiter and it's four large moons. It is what can be seen with a decent refracting spyglass or powerful binoculars which in terms of magnification power stands to the level of Galileo's scopes.

Camera Obscura (AstroMedia cardboard kit #2)

Jupiter Moons (zviktor22):


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