Museo Galileo
italiano
Virtual Museum
Multimedia
Optical images
Video   Text

 

Optically perceptible objects are those that give off light, either because they themselves produce it (these are called light sources) or because they receive light from sources and then diffuse it. An optical system gathers incoming light in its opening and directs the light to form an image—i.e., a purely optical reproduction of the object from which the light originates. The image is made of light and can often be seen by placing a screen (such as a sheet of paper) in its path. In this case, the image is called "real." The light travels beyond the real image, spreading and blurring the shape.

Alternatively, the image formation may be merely presumed: this time, the screen will capture the light but not the actual shape of the object. Such images are called virtual. To be displayed—for example, on photographic film, a television-camera sensor, or the retina of the eye—an image must be real. To form a real image, the entire optical system needs to focus.

The eye is equivalent to a converging lens with a focal length of 2 centimeters. The telescope is an afocal system. When the eye is combined with the telescope, the resulting optical system focuses, forming a real image on the retina. The ratio of the size of an image generated with the telescope to the size of an image produced without an instrument is called the magnification.

Objects
Amici I telescope

Amici I telescope

Inv. 3795
Giovanni Battista Amici, Italy, first half 19th cent.

Amici II telescope

Amici II telescope

Inv. 345
Giovanni Battista Amici, Italy, first half 19th cent.

Astronomical telescope

Astronomical telescope

Inv. 404
Dollond firm, London, 19th cent.

Binocular telescope

Binocular telescope

Inv. 2563
Chérubin d'Orléans, French, ca. 1675

Eyepiece lens

Eyepiece lens

Inv. 2573
Eustachio Divini, Rome, 1665

Eyepiece lens

Eyepiece lens

Inv. 2585
Ippolito Francini or Evangelista Torricelli or Jacopo Mariani [attr.], Florence, 1640-1660

Eyepiece lens

Eyepiece lens

Inv. 2584
Ippolito Francini or Evangelista Torricelli or Jacopo Mariani [attr.], Florence, 1640-1660

Eyepiece lens

Eyepiece lens

Inv. 2574
Eustachio Divini, Rome, 1666

Galileo's telescope

Galileo's telescope

Inv. 2427
Galileo Galilei, Italian, ca. 1610

Galileo's telescope

Galileo's telescope

Inv. 2428
Galileo Galilei, Italian, late 1609 - early 1610

Gregorian telescope by Selva

Gregorian telescope by Selva

Inv. 1419
Domenico Selva or Lorenzo Selva, Venice, 18th cent.

Lady's telescopes

Lady's telescopes

Inv. 3725
Maker unknown, second half 18th cent.

Lens

Lens

Inv. 2545, 2710/bis
Benedetto Bregans (lens), Francesco Spighi, Gaspero Mazzeranghi (mount), Lens: Dresden / Mount: Florence, Lens: 1690 / Mount: 1767

Newtonian telescope

Newtonian telescope

Inv. 2707
Leto Guidi, Italy, 18th cent.

Newtonian telescope

Newtonian telescope

Inv. 2710
Maker unknown, 18th cent.

Newtonian telescope

Newtonian telescope

Inv. 2709
Maker unknown, 18th cent.

Objective lens

Objective lens

Inv. 2571
Evangelista Torricelli, Florence, 1646

Objective lens

Objective lens

Inv. 2587
Giuseppe Campani, Rome, 1665

Objective lens

Objective lens

Inv. 3397
Giovanni Battista Amici [attr.], Italy, first half 19th cent.

Objective lens

Objective lens

Inv. 2632
Jacopo Mariani, Florence, 1660-1670

Objective lens

Objective lens

Inv. 2572
Evangelista Torricelli, 1643

Octagonal telescope

Octagonal telescope

Inv. 2553
Eustachio Divini, Rome, 1664

Octagonal telescope

Octagonal telescope

Inv. 2557
Eustachio Divini, Rome, 1674

Repeating circle

Repeating circle

Inv. 576
Georg Friedrich von Reichenbach, Munich, first half 19th cent.

Telescope

Telescope

Inv. 3090
Maker unknown, Italian, first half 18th cent.

Telescope

Telescope

Inv. 3377
Maker unknown, 1650-1670

Telescope for Torricelli's lens

Telescope for Torricelli's lens

Inv. 2554
Evangelista Torricelli (Objective) / Tube: maker unknown, Objective: 1647 / Tube: second half 18th cent. (?)

Telescope with accessories

Telescope with accessories

Inv. 3340
François de Baillou, Italian, 1764

Terrestrial telescope

Terrestrial telescope

Inv. 2548
Jacques Tendre de Moulina, French?, first half 18th cent.

Terrestrial telescope

Terrestrial telescope

Inv. 2550
Giovanni Battista Magnelli, Italian, 1695

Terrestrial telescope

Terrestrial telescope

Inv. 2552
Eustachio Divini, 1660-1670

Terrestrial telescope

Terrestrial telescope

Inv. 2556
Giuseppe Campani, Rome, 1666

Terrestrial telescope

Terrestrial telescope

Inv. 2560
Maker unknown, Italian, late 17th cent.

Terrestrial telescope

Terrestrial telescope

Inv. 2562
Johann Wiesel [attr.], German, ca. 1650

Terrestrial telescope

Terrestrial telescope

Inv. 3185
Giuseppe Campani, Italian, 1665

Terrestrial telescope

Terrestrial telescope

Inv. 3639
Paolo Belletti, Italian, 1689

Terrestrial telescope

Terrestrial telescope

Inv. 3549
Maker unknown, Italian, first half 18th cent.

Terrestrial telescope

Terrestrial telescope

Inv. 3493
Maker unknown, Italian, second half 17th cent.

Terrestrial telescope

Terrestrial telescope

Inv. 3458
John Marshall [attr.], English, late 17th cent.

Terrestrial telescope

Terrestrial telescope

Inv. 3339
Leonardo Semitecolo, Italian, second half 18th cent.

Terrestrial telescope

Terrestrial telescope

Inv. 2564
John Marshall [attr.], English, 1690-1720

Terrestrial telescope

Terrestrial telescope

Inv. 2561
John Marshall [attr.], English, 1690-1720

Terrestrial telescope

Terrestrial telescope

Inv. 2558
Maker unknown, English, early 18th cent.

Terrestrial telescope

Terrestrial telescope

Inv. 2551
Giuseppe Campani, Rome, ca. 1664

Terrestrial telescope

Terrestrial telescope

Inv. 2549
Maker unknown, English or German?, first half 18th cent.

Walking stick telescope

Walking stick telescope

Inv. 2547
Maker unknown, late 17th cent. - first half 18th cent.