Most historians credit Dutch eyeglass maker Hans Lippershey with inventing the first telescope in 1608. In 1671, Isaac Newton invented a telescope that formed images by reflecting light with a curved mirror. By the end of the 1800s, scientists were looking farther and farther into the universe. Today's telescopes map the universe past and present, helping astronomers figure out its history and its future. 
There are two main types of telescopes, reflecting telescopes and refracting telescopes.
Reflecting Telescopes
The reflecting telescope uses mirrors and convex lenses to collect and focus light. Figure 13A shows the path of light through a reflecting telescope. Light from a distant object strikes a large concave mirror and is brought to a focus. This focused light is reflected by an angled mirror and forms a real image. The convex lens of the eyepiece then enlarges the image.
Refracting Telescopes
The refracting telescope uses convex lenses to collect and focus light. Light from a distant object enters the telescope by passing through a convex lens called the objective lens. The convex lens forms a real image at its focal point inside the telescope. A convex lens in the eyepiece then magnifies this real image. As you look through the eyepiece, you see an enlarged, upside-down, virtual image of the real image. Figure 13B shows the path of light through a refracting telescope.
Figure 13 The two main types of telescopes use combinations of mirrors and lenses to magnify images of distant objects. A The reflecting telescope uses a large concave mirror to focus the incoming light rays. B The refracting telescope uses a series of lenses to focus light from distant objects.
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