Galileo's Telescope

From Antiquity to the 16 th century, instruments for astronomical observation underwent minimal changes. Apart from some perfecting touches devised by individual astronomers, they consisted of revolving frames fitted with graduate scales and appropriate sights. These instruments, which equipped the major Islamic and European observatories, allowed the positions of the heavenly bodies to be precisely determined. Using quadrants, sextants, rings and rules of various kinds and sizes, the astronomer carried out his work, which consisted of updating the numerical parameters that governed the motion of the stars.

In this scientific environment, apart from the general structure of the Universe in which an astronomer could believe, the heavens were considered to have been fully explored. At the start of the 17 th century it was thought that all of the existing planets were known and all of the fixed stars had been identified and catalogued. Not even the most attentive and systematic observation of the sky would ever have revealed anything new, apart from some sporadic comet or nova. No one could ever have imagined what wondrous new things were about to be revealed by an instrument created by inserting two eyeglass lenses into the ends of a tube.

Galileo and the Telescope

• Galileo's Telescopes
• Galileo's Observations
• Further Information
• Questions

The science of astronomy took a huge leap forward in the first decade of the 1600s with the invention of the optical telescope and its use to study the night sky. Galileo Galilei did not invent the telescope but was the first to use it systematically to observe celestial objects and record his discoveries. His book, Sidereus nuncius or The Starry Messenger was first published in 1610 and made him famous. In it he reported on his observations of the Moon, Jupiter and the Milky Way. These and subsequent observations and his interpretations of them eventually led to the demise of the geocentric Ptolemaic model of the universe and the adoption of a heliocentric model as proposed in 1543 by Copernicus.

Galileo's drawings of phases of the Moon.
Question: What features are visible here that cannot be seen with the unaided eye?

Galileo's Telescopes

The basic tool that Galileo used was a crude refracting telescope. His initial version only magnified 8x but was soon refined to the 20x magnification he used for his observations for Sidereus nuncius. It had a convex objective lens and a concave eyepiece in a long tube. The main problem with his telescopes was their very narrow field of view, typically about half the width of the Moon.

Galileo's drawing of the optical path of his telescope

The earliest known sketch of a telescope, August 1609.

One of Galileo's telescopes. The focal length is 1330 mm with a 26 mm aperture, it magnifies 14x. It has an objective bi-convex lens and a plano-concave eyepiece.

Galileo's Observations

Galileo made several key discoveries through his systematic use and refinement of the telescope.

The Moon

According to Aristotelian principles the Moon was above the sub-lunary sphere and in the heavens, hence should be perfect. He found the "surface of the moon to be not smooth, even and perfectly spherical,...,but on the contrary, to be uneven, rough, and crowded with depressions and bulges. And it is like the face of the earth itself, which is marked here and there with chains of mountains and depths of valleys." He calculated the heights of the mountains by measuring the lengths of their shadows and applying geometry.

One of Galileo's lunar drawings.
Note the craters, mountains and mare or "seas". The terminator between lunar day and night is clearly seen down the centre.

Moons of Jupiter

Observations of the planet Jupiter over successive night revealed four star-like objects in a line with it. The objects moved from night to night, sometimes disappearing behind or in front of the planet. Galileo correctly inferred that these objects were moons of Jupiter and orbited it just as our Moon orbits Earth. For the first time, objects had been observed orbiting another planet, thus weakening the hold of the Ptolemaic model. Today these four moons are known as the Galilean satellites; Io, Europa, Ganymede and Callisto.

Galileo's drawings of the moons of Jupiter of successive nights

The Phases of Venus

Venus was observed to go through a sequence of phases similar to the Moon. This could not be explained in the Ptolemaic model but could be accounted for by either the Sun-centered Copernican model or the Earth-centered Tychonic model that had the other planets orbiting the Sun as it orbited the Earth. Galileo rejected Tycho's model as an unnecessary hybrid and used the discovery to consolidate his support of the Copernican model.

Sunspots

Along with contemporaries such as Thomas Harriot, David Frabicius and Christoph Scheiner, Galileo observed dark regions that appeared to move across the surface of the Sun. Debate centered on whether these were satellites of the Sun or actual spots on its surface. Galileo, in his Letters on Sunspots supported the sunspot interpretation and used it to show that the Sun was rotating. Its blemishes and imperfections again undermined the Aristotelian ideal of a perfect cosmos.

"Appendages" on Saturn

Galileo noted two appendages from the sides of Saturn. These disappeared then later reappeared. It was not until 1656 that the Dutch scientist, Christiaan Huygens correctly described them as rings.

Stars in the Milky Way

Even through a telescope the stars still appeared as points of light. Galileo suggested that this was due to their immense distance from Earth. This then eased the problem posed by the failure of astronomers to detect stellar parallax that was a consequence of Copernicus' model. On turning his telescope to the band of the Milky Way Galileo saw it resolved into thousands of hitherto unseen stars. This posed the question as to why there were invisible objects in the night sky?

More stars are resolved in this drawing by Galileo of the Pleiades than are visible to the unaided eye.

Further Information

1. An excellent online source for all things related to Galileo is: The Galileo Project. It is hosted by Rice University and includes his writings, details on his experiments and observations and links. It is also the source for the image of Galileo at the top of this page.
2. Another worthwhile site is The Art of Renaissance Science: Galileo and Perspective. It has a wealth of diagrams matched with clear. concise text. There are some animations of his experiments.
3. The Institute and Museum of the History of Science in Florence has a wealth of detail on the history of astronomy including Galileo's work. Their new website is worth exploring. Much of it is in English although some sections, including an excellent simulation of early telescopes, is only available in Italian at present. They also have an excellent new site: Galileo's Telescope, the Instrument that Changed the World.
4. Afocal CCD Images Through a Galilean Telescope is an excellent resource that provides CCD images that approximate what the human eye would see through a Galilean telescope. It has images of the Sun, Moon, Venus, stars and nebulae. The site provides historical background and technical details.
5. Galileo's Sidereus nuncius or The Sidereal messenger is available in translation by A. van Helden from University of Chicago Press, 1989.
6. The Cambridge Illustrated History of Astronomy, ed Michael Hoskin, Cambridge University Press, 1997 provides a wealth of information and diagrams and is an authoritative yet readable guide to the topic.
7. The Sleepwalkers by Arthur Koestler is a classic book dealing with the development of astronomical thought up to the time of Newton.

There are numerous other books and web sites covering Galileo's work and the history of astronomy.

Questions

1. Why was the telescope an advance over naked-eye astronomy?
2. What did Galileo's observations of the Moon reveal?
3. What was the significance of Galileo observing phases of Venus?
4. How did Galileo's observations help undermine the existing paradigm of the Ptolemaic model of the Universe and Aristotle's physics?

Google Wears Galileo's telescope

Doodle 400th Anniversary of Galileo's Telescope

Galileo's telescope will be online on every google homepage

If you visit Google.com today, you will notice a special logo that looks like a telescope, It is a depiction of the Galileo's telescope .


Click the google logo to learn more about Nikola Tesla.


for more information visite:

http://galileos-telescope.blogspot.com/

Galileo's Telescope Travels Far, Sees Farther

Enlarge Melisa Goh/NPR

Franklin Institute's chief astronomer Derrick Pitts (right) points out details of Galileo's telescope to visitors.

Instruments of revolution can appear deceivingly simple. With a bit of wood, copper wire and paper, Galileo fashioned a telescope that opened the skies for discovery.

The telescope had a magnifying power of 20. By today's standards, that's not very strong, but in 1609, Galileo's telescope surpassed all others. It was powerful enough for him to detect the moon's rough surface, Venus' phases, and Jupiter's moons.

Galileo actually tracked and measured the movement of Jupiter's satellites. His observations gave further evidence of the Copernican theory that the sun was the center of the universe.

For the first time ever, Galileo's research telescope has traveled across the Atlantic. It's at the center of the exhibit, Galileo: The Medici and the Age of Astronomy at the Franklin Institute in Philadelphia. The museum's chief astronomer, Derrick Pitts, says the research telescope symbolizes Galileo's "dogged determination" to understand the universe.

A clear case protects the telescope, but visitors can get close enough to brag that they have looked through Galileo's telescope. They won't see the night sky, however — the telescope points toward the museum's ceiling.

telescopes History , Galileo and telescope ,Galileo's telescope

The first inhabitants of the world were forced to examine their daily activities and annual change of light and darkness and cold and heat. In history there are few great men who made a great contribution to astronomy, one of them, Galileo Galilei and his work with the telescope was.

If you are looking at the telescopes of today, we mainly work with the telescope of Galileo or the other or a telescope of Newton. These men have such an impact in astronomy and telescopes, invented still the same types of telescopes for men, we do!

Full name of Galileo Galilei Galileo was an Italian physicist and astronomer. Galilei born in Pisa, February 15, 1564 and lived for 78 years until 1642, when he died. Right now he has made some progress in astronomy, we now know the name of Galileo.

Galileo has not only the advances in astronomy, it is noted with the invention of the thermometer! Telescope Galileo Galilei was the first observations of the moon and its growing, sun, planets and stars to make.

Most of the time of Galileo and energy was in mathematics and he spent the most time. In fact, he became professor of mathematics at the University of Pisa in 1589. What did Galileo was switched from mathematics and physics at a major interest in astronomy, when he heard the telescope in the Netherlands in 1609.

Ever since Galileo immediately focused his attention on building his own telescope. Galileo Galilei telescope was developed, and immediately began to see in the sky. He published his results in Starry Messenger. The Starry Messenger one years later, in 1610. The book was a feeling across Europe, he made his famous telescope.

Galileo Galilei, the telescope and its conclusions are not always so rosy, however. At this point, the common idea was decided upon by the Church, that the universe revolved around the earth! Copernicus had a new theory, the Copernican theory holds that the universe does not revolve around the earth. Galileo had this belief as well, and he had a big scandal with the church. The church declared that Galileo was considered heretical and instructed to abandon the Copernican theory.

In 1632 published a book entitled Dialogue Concerning the Two Chief World Systems. In the book Galileo Galilei telescope was used to show how the concept was borne from the church wrong. He led Galileo to be sentenced to life imprisonment. The conviction was overturned and arrest for the rest of his life building.

Galileo was a great inventor and has given the world some of the greatest inventions. In a telescope, Galileo Galilei, the light enters through a tube with a front convex lens. The light is still a concave lens in the eyepiece focus, before meeting his eyes with an enlarged portion and vertically.

Galileo Galilei is a telescope that we can never forget. It was an invention which has in its time a planet (Saturn shown), who has ears! Within 2 years of the telescope by Galileo, it gives us very precise information about the orbits of 4 satellites of Jupiter. Galileo also gave us good information about sunspots on the sun.

Galileo’s refracting telescope (1609)

Get to the root of it

Galileo’s refracting telescope (1609)

Galileo’s refractor used two lenses to concentrate the light from celestial objects, delivering more light to the human eye than it can gather on its own. The light was refracted through a spherical lens, forming an image.

The spherical shape of Galileo’s primary lens made the images blurry. The lens also split light into colors, creating a fringe of color around bright objects.