Wow! Look at that! You can see Haley’s Comet from here and it’s not even blurry. This reflecting telescope works so much better than that old refracting telescope.

For hundreds of years, telescopes were the only things people could use to study the sky. Today we use telescopes to study distant stars and galaxies. We do use space probes, but they can only go so far out in space and they take a very long time to get there.

A telescope is a device that allows you to look at an object that is far away or very faint, and it makes the object appear much closer to the person looking through it. Most telescopes work by collecting and magnifying light that was given off by stars or reflected by the surface of planets. This type of telescope is called an optical telescope. Optical telescopes use mirrors or lenses that collect the light and make the image appear larger.

In 1608 a Dutch optician (someone who makes lenses) named Hans Lippershy discovered that a distant object could be seen much clearer if it was looked at through concave and convex lenses. So he stuck two lenses in a tube and created the first telescope. About a year later Galileo, an Italian astronomer, made his own refracting telescope and discovered four moons orbiting Jupiter. Galileo also used his refracting telescope to map the surface of the moon.

In 1663 a Scottish astronomer named James Gregory designed a reflecting telescope, which bounced light rays off of the mirror instead of bending them like on a refracting telescope. From Gregory’s design, Isaac Newton built the first reflecting telescope in 1688. After Newton built the reflecting telescope, scientists discovered that better images were seen through the reflecting telescope instead of the refracting telescope because the mirror could make larger and clearer images of the object. The telescope reacted like this because the mirror simply reflects the light and the refracting telescope has to bend the light.

Refracting telescopes use glass lenses to bend light, magnify it, and bring it into focus. The convex lens is thickest at the center and thinner towards the edge. This shape allows the lens to bend the light at the edge of the lens at a greater angle than the light coming through the center, so all of the light rays come together at a point of focus.