Powers of a telescope - Northwestern Universityfaculty.wcas.northwestern.edu/.../telescopes... ·...

•  Powers of a telescope"–  Light Gathering Power"–  Resolving Power"–  Magnification "

•  Types of telescopes / Definition of telescope"–  Refractor"–  Reflector "

•  Atmospheric distortion"–  Seeing"–  Reddening and Extinction"–  Atmospheric lines "

Lecture 7, Part I: Telescopes"

Yerkes Observatory, circa 1890"

Light Gathering"Want a large

collecting area or “light bucket.”"Flux ratio = (D2/D1)2

m1 - m2 = -2.5 x log(Flux ratio)"

Deye = 5 mm = 5x10-3 m"Dtel = 1 m "

(Dtel/Deye)2 = (1m / 5x10-3m)2 = 4x104"

m1 – m2 = -2.5 x log(4x104) = -11.5 mag"

For Example:"

Light Gathering"Want a large

collecting area or “light bucket.”"Flux ratio = (D2/D1)2

m1 - m2 = -2.5 x log(Flux ratio)"

Deye = 5 mm = 5x10-3 m"Dtel = 1 m "

(Dtel/Deye)2 = (1m / 5x10-3m)2 = 4x104"

m1 – m2 = -2.5 x log(4x104) = -11.5 mag"

For Example:"

Light Gathering"Want a large

collecting area or “light bucket.”"Flux ratio = (D2/D1)2

m1 - m2 = -2.5 x log(Flux ratio)"

Getting above the atmosphere is even better!"

Deye = 5 mm = 5x10-3 m"Dtel = 1 m "

(Dtel/Deye)2 = (1m / 5x10-3m)2 = 4x104"

m1 – m2 = -2.5 x log(4x104) = -11.5 mag"

For Example:"

D"

slit" screen"Resolving Power Diffraction"The wave nature of

light."

arcsecond"

For Example:"

Δθ = λ/D"

The atmosphere messes up resolution too…"

Wave Nature of Atoms"

Telescopes"•  Refractor:"

•  Reflector: "

Telescopes"Common reflecting telescopes include"

•  Newtonian"•  Cassegrain"•  Coudé"

Photometry"

Spectroscopy"

The Telescopes of Mauna Kea"

Atmospheric distortions:“Seeing”"

Adaptive Optics"

Atmospheric distortions:“Seeing”"

Adaptive Optics"

•  Young stars"•  Bound orbits"•  Probe the

potential"•  Fix the position "•  No assumptions"•  Isotropic"

Gillessen et al 2010"

scale ~ few light days"

The S Stars"

•  Young stars"•  Bound orbits"•  Probe the

potential"•  Fix the position "•  No assumptions"•  Isotropic"

Gillessen et al 2010" The S Stars"

Hubble Space Telescope"

Δθ = (2.06x105)(5.5x10-7 m) / 1m

= 1.1x10-1 arcsec"

recall: 1 radian = 206,264.806 arcsec"

James Webb Space Telescope"

The Spitzer Space Telescope"

Sofia

Radio Telescopes"

Radio Telescopes"

Interferometers"

Radio Telescopes"

Radio Telescopes"

Radio/Sub-mm Telescopes: ALMA"

X-ray Telescopes"

X-ray Telescopes"

X-ray Spectroscopy"