lecture 4: telescopes
telescope basics
assumptions
parallel rays of light
stars are point sources
focus
primary focus
cassegrain focus
nasmyth focus
coude focus
telescope mounts
equatorial/polar
alt-az
abberations
spherical aberration: on-axis aberration
focal length & focal plane
coma: off-axis aberration
astigmatism
distortion
field curvature
vignetting
chromatic aberration
quantifying the performance
plate scale: S = Fθ
focal ratio
R = F/D
measures how quick can we get light
fast optics: small f/R
field of view
point spread function(PSF)
describe how the telescope responds to a point source
diffraction
airy disk:θ = 1.22λ/d
reyleigh criterion: resolution limit = θ
seeing
adaptive optics(AO)
SNR
signal to noise ratio
longer exposure time -> higher SNR