TELESCOPES Where do we put telescopes to have the best viewing conditions? 1. On Earth: CLEARHIGHDRYCOLDDARK Problem with Telescopes on Earth? Problem: Particles of all sorts in the atmosphere block and cloud the view Particles of all sorts in the atmosphere block and cloud the view 2. In Space Solves atmosphere problem CLEAR VIEW! Examples: Hubble, Cobe, Iras Problem with telescopes in space? Theyre in space! Hard to get to Hard to repair EXPENSIVE!!! Functions of a Telescope 1. C ollect Light 2. M agnify Images 3. S eparate Distant Objects 4. U se as a Camera OPTICAL TELESCOPES (USE VISIBLE LIGHT) Two types: 1. Refractor BENDS LIGHT Invented by Hans Lippershey in 1608 Refined by Galileo in 1609 Galileo demonstrating his telescope 2. Reflector USES MIRRORS Tololo Observatory - Chile TYPE 1 REFRACTING TELESCOPE How does it work? a. It bends light to create an image b. It uses two lenses 1. eyepiece (ocular) lens - small 2. objective lens - large Draw it! Type 2 Reflecting Telescope a. Invented by Isaac Newton in 1668 b. Uses two mirrors Objective Mirror Large Secondary (flat) mirror Small Secondary (flat) mirror Small c. Can be VERY LARGE 40 ft - 50 ft diameter objective mirror! Draw It! Advantages of a reflector 1. You only need to prepare one side of the mirror. (on a refractor the lens has two sides) cheaper and distortion is less of a problem. 2. The whole back of the mirror can be supported, therefore can be made very LARGE Non-optical Telescopes 1. Radio Telescopes a. Location Earth (atmosphere does not affect radio waves) b. Structure Large metal dish c. Size very large because radio waves have a very long wavelength d. Arrays sets of multiple radio telescopes that allow for more data to be gathered. Ex VLA (very large array) in Socorro, New Mexico 27 dishes. SETI Search for Extra-Terrestrial Intelligence looking for intelligent radio signals looking for intelligent radio signals Other Non-Optical Telescopes (all are satellites) a. Infrared IRAS launched 1983 b. Microwaves COBE Cosmic Background explorer. Discovered evidence of the Big Bang. Launched 1981 COBE Image of CBR c. X-Rays Chandra Launched 1999 Cassiopeia Super Nova Black Hole Crab Nebula Saturn d. Gamma Rays GRO Gamma Ray Observatory Milky Way