The Galileoscope™ is a high-quality, low-cost telescope kit developed for the International Year of Astronomy 2009 by a team of leading astronomers, optical engineers, and science educators. No matter where you live, with this easy-to-assemble, 50-mm (2-inch) diameter, 25- to 50-power achromatic refractor, you can see the celestial wonders that Galileo Galilei first glimpsed 400 years ago and that still delight stargazers today. These include lunar craters and mountains, four moons circling Jupiter, the phases of Venus, Saturn's rings, and countless stars invisible to the unaided eye.

The International Year of Astronomy 2009 by Endorsed by the United Nations and UNESCO, IYA2009 celebrates astronomy's contributions to society and culture, helps "connect the dots" between science and technology and prosperity, and aims to stimulate worldwide interest, especially among young people, in science.  After all, anyone with a telescope can see what Galileo saw.

But not everyone has a telescope, especially in less developed parts of the world. To enable more people in more places to personally experience the wonders of the universe, the IYA2009 developed a remarkably inexpensive, very-high-quality, easy-to-use refractor. With this new instrument, called the Galileoscope, children and adults can learn how telescopes work and repeat for themselves the spectacular observations made by Galileo beginning in 1609.

The Galileoscope™ is a refracting telescope, or refractor: a long tube with a big lens (the objective) at the front end and a small lens (the eyepiece) at the back end. The great Italian scientist Galileo's telescopes were refractors, too, but the Galileoscope improves upon his 400-year-old design in several important ways, as described below.

Here are the instrument's key optical characteristics:

Objective diameter:

50 mm (2 inches)

Objective focal length:

500 mm (f/10)

Eyepiece focal length:

20 mm


25x (50x with Barlow)

Field of view:

1½° (¾° with Barlow)

Eyepiece eye relief:

16 mm (22 mm with Barlow)

Eyepiece barrel diameter:

1¼ inches (31¾ mm)

The field of view is the angular diameter of the circle of sky you see when you look into the telescope's eyepiece. The full Moon is about ½° wide, so the Galileoscope's field at 25x is three Moons wide, just big enough to encompass the splendid Pleiades star cluster in Taurus, one of the objects Galileo marveled at 400 years ago. If you double the magnification to 50x using the included Barlow lens, the width of the field of view is correspondingly halved.

Eye relief is the distance behind the eyepiece that you need to put your eye to see the entire circular field of view. The Galileoscope's ample eye relief of 16 mm at 25x and 22 mm at 50x should enable anyone, including children, to observe comfortably with or without eyeglasses.

The last entry in the table is significant. We've designed the Galileoscope to accept accessories with the standard 1¼-inch barrel common to most commercial telescopes. This means that you can substitute your own eyepieces of various focal lengths for the supplied 20-mm eyepiece, giving you additional options for magnification and field of view. (The magnification of a telescope is the focal length of the objective divided by the focal length of the eyepiece in the same units; with a given objective, eyepieces with shorter focal lengths give higher powers, and vice versa.)

In addition to the main eyepiece, the Galileoscope comes with another plastic achromat that can be used in either of two ways: as a 17x eyepiece in the Galilean configuration, or as a 2x Barlow lens to double the magnification of the Galileoscope to 50x in its normal Keplerian configuration.

The Galileoscope forms the basis of this optics educational program.

Links to Galileoscope:

Buy the Dobsonian-like mount for this telescope for only R125 ('see accessories/mounts/light table mount'

Please enquire when stock is indicated as zero.  Availability is typically within 2 months - please enquire.

Add to Cart:

  • Model: IYA_GScope_1
  • Shipping Weight: 0.95kgs
  • 60 Units in Stock
  • Manufactured by: Crux Astronomy

This product was added to our catalog on Tuesday 17 March, 2009.

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