1. Telescopes

2. Telescope History
Galileo Galilei built first refractive telescope in 1609
Isaac Newton built the first reflective telescope in 1668

3. 1st Reflecting Telescope by Isaac Newton

4. Optical Telescopes Telescopes that contain mirrors, lenses, or both
Three properties:
Light-gathering power
Resolving power
Magnifying power

5. Optical Telescopes Telescopes with larger mirrors/lenses:
Can“see”farther into space
Have greater resolution
Magnification can be changed by using different eyepieces
Usually placed on mountain tops to reduce city lights

6. Refracting Telescopes
Telescope uses two lens to bend or refract light
Simplest of all telescopes
First refracting telescope capable of magnifying objects 30 times.

7. Objective Lens Most important lens is the objective lens
Bends the light from a distant object and focuses the light at the focus to produce an image
The objective lens produces a very small, bright image of an object
Focus= central point
Focal length= distance between the focus and the objective lens

8. Eyepiece Lens The second lens used in a refractive telescope
Eyepiece magnifies image produced by the objective lens

9. Simple Refracting Telescope

10. Disadvantages
Shorter wavelengths of light are bent more than the longer ones
Chromatic aberration:
Weakens image and creates a halo of color around it
When red light is in focus, a bluish halo appears.
Very hard to produce a large piece of high-quality, bubble-free glass

11. Yerkes Observatory Largest Refracting Telescope

12. Yerkes Observatory Williams Bay, Wisconsin

13. Refracting Telescope at Lick Observatory Southern California

14. Lick Observatory

15. Reflecting Telescopes
Uses a concave (curved) mirror that focuses the light in front of it
Mirror is coated in a highly reflective material, an aluminum compound
Two mirrors- one large & concave and one small & flat

16. Reflecting Telescope

17. Advantages
No Chromatic aberration because reflected light is not dispersed into its component colors.
Glass does not need to be high-quality because light does not pass through it.
Disadvantage–secondary mirror blocks some light entering the telescope.

18. Mount Palomar Observatory California

19. Mirror for Hale Telescope at Mount Palomar Observatory

20. Hale Telescope

21. Keck Telescopes World’s Largest Reflecting Telescopes Hawaii

22. Schematic of Keck Multiple Mirros Telescope (MMT)

23. Kitt Peak Observatory Arizona

24. La Palma Observatory Canary Islands, Spain

25. McDonald Observatory Texas

26. Cerro Tololo Observatory Chile

27. Invisible Light
Stars produce light wavelengths that are not visible to our eyes
Gamma rays, X-rays, ultraviolet radiation, infrared radiation, and radio waves
Most of these can not get past our atmosphere… so we must get our cameras above it!

28. Radio Telescopes These big dishes are used to detect radio waves
Focuses incoming radio waves on an antenna and transmits these to an amplifier.

29. Radio Signals Radio signals are weak so it requires a very large dish
These telescopes have poor resolution
Radio Interferometer= Wire several telescopes together

30. Advantages
Less affected by turbulence in the atmosphere, clouds, and weather
No protective dome is required = cheaper
Can be used and “viewed” 24 hours a day
Radio signals can pass through intersteller dust clouds

31. Disadvantages Can be affected by human-made radio interference
Usually placed in valleys to block interference

32. Largest Radio Telescope in World Arecibo, Puerto Rico

33. VLA Radio Telescope Socorro, New Mexico

34. VLA

35. Space Telescopes
Orbit above Earth’s atmosphere and produce clearer images

36. Hubble Space Telescope
Built by NASA and sent in April 1990
10 billion times more light-gathering power than the human eye
Given us amazing images of space

39. Other Space Telescopes
Chandra X-Ray Observatory
NASA uses to study X-rays
Launched in 1999
Gather data about black holes
Compton Gamma-Ray Observatory
Used to study visible light and gamma rays
In 2018, NASA will launch James Webb Space Telescope to study infrared radiation
Run into many obstacles and budget problems