As glassmaking became more refined and lenses were made of greater quality, someone wondered what would happen if you placed two lenses in a row. The result of the experiment eventually became the refracting telescope...

The exact date of the building of the first refractor telescope is not known, but there is strong documentary evidence for the presence of refracting telescopes in England as early as the Sixteenth Century, though they did not become widespread in Europe until the Seventeenth in the Netherlands. Hans Lipperhey (whose patent was rejected as being too easy to copy) and Zacharias Janssen of the Netherlands, both claim the invention of the revolutionary device that caused a whole new world view and spread all over Europe.

Whoever the inventor, the original telescope consisted of both a convex and concave lens so the image could be viewed the right way up. In 1909, Galileo refined the design by putting distance between the two lenses, refining the image and reducing the rainbow effect of refracting light that had previously surrounded distant objects. Galileo continued to refine the telescope improving the magnification from a power of three to a power of thirty-three. In 1910 he used the telescope to discover the moons of Jupiter, sunspots and the craters, hills and valleys of the moon. His observations helped to challenge the view that the Earth is the center of the universe.

Today telescopes that can match and improve on the observations of Galileo are widely available. Created of a long tube of wood or metal with a lens at both ends and an eyepiece, the tube keeps the lenses free from dust, debris and water. The two lenses work in the same way as the original, focusing and refracting the light that is then magnified by the eyepiece producing a clear image.

Modern telescopes are expensive and have a high resolution. They are able to see in great detail binary stars and planets as well as a large number of other objects, though they are less useful for looking at very large distant objects such as nebulae and galaxies.