- telescope: light bucket that captures photons and focuses them for analysis
- optical telescopes collect what is visible to naked eye; refract and reflect
- refraction: bending of a beam of light as it passes from one transparent medium into another
- refracting telescope: uses lens to gather and concentrate a beam of light
- reflecting telescope: uses curved mirror to focus incoming light
- prime focus: focus of primary mirror
- astronomical telescopes used to make images of field of view
- often magnified by lens to be seen by human eye
- chromatic aberration common problem with refracting telescopes
- some light absorbed which hinders infrared and UV observations
- large lenses can hinder viewing
- Newtonian telescope: light is intercepted before it reaches prime focus and is deflected to side eye piece
- Cassegrain telescope: secondary mirror used to reflect into equipment
- Hubble space telescope still functioning today
5.2
- light gathering power and resolving power have increased over time
- collecting area: total area capable of gathering radiation
- perceived brightness is proportional to area of mirror
- telescopes are much easier to manufacture now
- infrared telescopes are becoming more and more popular
- very large telescope (VLT) in Chile
- angular resolution aides in distinguishing objects
- diffraction hinders ability to focus on specific objects
- diffraction-limited resolution: best angular resolution of light
5.3
- charge-coupled devices: electronic detectors
- pixels: 2 dimensional array of many tiny picture elements
- CCD chips used in many astronomical telescopes
- more efficient than photo plates
- image processing used to reduce background noise in pictures
- computers help compensate for instruments not available
- large reflectors used o form narrow fields of view
- ccd make telescope basically used as a high power camera
- photometry is brightness
- filters used to limit measured wave lengths
- photometer: measures total amount of light received in field of view
- spectrometer: used to measure spectrum of incoming light
- can be studied in real time or stored on ccd for later usage
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