reflecting Telescopes
- mirrors can be made very large
- only 1 surface needs to be good
- can be supported from the back
Light gathering power
- equal to the collecting area ?r2, where r is the radius
- eye pupil radius 0.5 cm vs. Hubble radius 100 cm
- radius 200 times bigger
- area 40,000 times bigger
- can see things 40,000 times (11 magnitudes) fainter
- picture of Hubble primary and optics, Gemini 8 m mirror
Spatial resolution - sharpness of image
- very important -- take off glasses and look around
- Fundamental limit from intereference of light waves
- waves from different parts of mirror can’t combine totally