18-3 pgs  IN: What is a telescope? How is it used?

 Telescope – an instrument that collects electromagnetic radiation from the sky and concentrates it for better observation.

 Electromagnetic spectrum – all the wavelengths of electromagnetic radiation. From stars.

Multiwavelength Astronomy - Our Galaxy: The Milky Way

 Refracting telescope – uses a set of lenses to gather and focus light.

 Refracting telescope Size is limited Large lens can distort image

 Reflecting telescope – uses curved mirrors to gather and focus light.

 Reflecting telescope Mirrors can be made very large Allow all colors to be seen.

 Keck Telescope, Hawaii

 The light gathered can be affected by the atmosphere.  The dust and dirt in the atmosphere is what cause stars to “twinkle”.

 Telescopes are place in dry areas to avoid water vapor in the air.  Mountaintops are also good places because or the higher elevation. This puts the telescope above pollution and increases the visibility of stars.

hubblesite org To avoid the atmosphere, scientists put telescopes in space.

 Astronomers are interested in all forms of electromagnetic radiation because different objects radiate at different wavelengths. Radio Telescopes Receive radio waves Hopkins Telescope Detects UV wavelenghs

 OUT: Name one way in which refracting and reflecting telescopes are similar and one way they are different.