AST 111 Lecture Notes - Lecture 9: Refraction, Secondary Mirror, Chromatic Aberration

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21 Sep 2015
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AST 111: Lecture 9-Optics and Telescopes
Refracting Telescope
- Uses lenses
- Designed by Galileo
- Refraction is the bending of light
- General properties of telescopes:
oLight gathering power: larger telescopes collect more light hence can
show fainter objects
oMagnification: increase the apparent size
- All telescopes that use lenses are subject to chromatic aberration
oThe light of different colors cannot come to the same foucs
Reflecting Telescope
- Uses mirrors
- Designed by Newton
- Newtonian- 2 mirrors
- Prime- 1 mirror
- Cassegrain- Convex secondary mirror that reflects down the telescope tube
- Coude- multiple mirroros to focus light to a remote focal plane
Angular Resolution
- seeing things very close together in angles in the sky as separate objects