1. Telescopes Key Words Optical Telescopes: make use of electromagnetic radiation in the range of visible light Refraction Telescopes: use lenses Reflecting Telescopes: use mirrors Focal Length: the distance from the lens (or mirror) to the image formed of a distant light source

2. Telescopes Key Words Primary Lens: the main lens (the objective lens) of a refracting telescope Primary Mirror: the main mirror (the objective mirror) of a reflecting telescope Chromatic Aberration: the colour separation that occurs when light is refracted through a lens Radio Telescopes: make use of electromagnetic radiation in the range of radio waves

3. The Hubble Space Telescope

4. Edwin Hubble (1889-1953) American Astronomer 1919 offered a staff position at Mount Wilson Observatory, California Used the Hooker Telescope Demonstrated the existence of other galaxies Developed a system for classifying galaxies

5. Hubble’s Law: the greater the distance between any two galaxies, the greater their relative speed of separation “Hubble’s Law” helped establish that the universe is expanding

6. The Hubble Space Telescope (HST)

7. Idea for space telescope as early as the 1920s Received funding in the 1970s Carried into orbit April 1990 Collaboration between NASA and ESA

8. Problem with the Hubble The original mirror was incorrectly shaped Could not focus all light to one sharp point. Fuzzy halo. Servicing mission in 1993 Installed 2 new devices: like “corrective eyeglasses”

9. Components of the HST

10. The numbers 370 miles (595km) from Earth 43.5 ft (13m) in length 14ft (4m) diameter 25500lbs (11000kg) 8 ft (2.5m) primary mirror weighs 1825lbs (826kg) 1ft (30cm) secondary mirror 5 scientific instruments on board 400million bites of info sent to Earth on a typical day 1000 astronomers involved in observations per year

11. The Webb Space Telescope Successor to the Hubble Space Telescope Tennis court sized Will detect infrared light. Will see it as clearly as Hubble’s visible light. Will orbit outside the orbit of the moon! Launch scheduled for later in the decade video