1. Optical Telescopes Telescopes that detect light waves from stars. This type of telescope uses lenses to bend and focus the light from stars. It was developed by Galileo.

2. Refracting Telescopes The refractor telescope uses a lens to gather and focus light more efficiently than the human eye

3. Refracting Telescopes Refraction--how lenses and prisms work  light slows down when it goes through matter  why your arm looks bent in a swimming pool A curved piece of glass forms a lens  focus of lens is where rays of light meet  refracting telescopes need at least two lenses, objective and eyepiece spacing between lenses has to be just right (why you need a focus adjustment)

4. Refracting telescope Focal point – all of the light is focused onto this point inside the telescope. Eye Piece Objective lens

5. Refracting Telescope

9. Reflecting Telescope This type of telescope uses mirrors to bend light. It was invented by Sir Isaac Newton.

10. Reflecting Telescopes Light passes through the tube and hits a concave mirror The curve in the mirror bends the light so that it bounces onto the flat mirror Flat mirror bounces the light so that it meets at the focal point (eye piece)

12. Clyde Tombaugh 1904 - 1997

14. Hale Telescope at Palomar Observatory

16. McDonald Observatory

18. Hubble Space Telescope

19. Hubble Space Telescope (HST) being deployed during the STS 31 flight.

20. Refraction Analogy

21. Yerkes Lens

22. The hunt for Planet X -1903-1916