Chapter 3: Telescopes

Goals Describe basic types of optical telescopes Explain why bigger is better for telescopes Describe how the Earth’s atmosphere effects observations Review benefits of radio astronomy Explain interferometry Discuss advantages of different regions of the spectrum

Chapter 3: Telescopes Because different regions of the electromagnetic spectrum have different wavelengths astronomers have to design different telescopes specifically for each region. The most well known is the optical telescope which comes in two flavors: 1) reflecting, 2) refracting. Advantages: Reflecting bigger cheaper all color Refractor better resolution

Chapter 3: Telescopes The size of the telescope determines how faint it can image an object and how small an object it can resolve. Light gathering power is proportional to the area. F  area

Chapter 3: Telescopes The smallest angle observable is related to the diameter  1/diameter

Chapter 3: Telescopes Various techniques try to increase the angular resolution of telescopes including interferometry, adaptive optics, and space based instruments.

Chapter 3: Telescopes While major observatories are built on high mountain tops or in space to remove as much seeing as possible.

Chapter 3: Telescopes Adaptive optics tries to modify the shape of the mirror to remove the “seeing” effects.

Chapter 3: Telescopes Radio Astronomy must use large antennae to collect radiation because the signal is so weak.

Chapter 3: Telescopes Interferometry combines two or more telescopes in such a way that the angular resolution depends on the separation of the two telescopes. While radio astronomers have used it for years, optical astronomers are just beginning to try.

Chapter 3: Telescopes Other regions like infrared, ultraviolet, Xray, etc must go the space because the atmosphere absorbs most of the energy.

Chapter 3: Telescopes Astronomers use the different regions of the spectrum because each region tells a different story. a) radio, b) infrared, c) visible, d) X-ray, e) gamma ray