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Telescopes - Tools of the Trade Keck telescope in Mauna Kea, Hawaii. Light Pollution. Large lens = more light = brighter image. Collecting Power α (proportional to) Area of the lens (or mirror).
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Telescopes - Tools of the Trade Keck telescope in Mauna Kea, Hawaii
Large lens = more light = brighter image Collecting Power α (proportional to) Area of the lens (or mirror)
The Collecting Power of a lens or mirror is proportional to the Area of the lens or mirror. Since Area is proportional to the Diameter2or Radius2we can write Collecting Power α Radius2 (Diameter2) CP α r2 If the size of the mirror or lens is doubled, the collecting power increases by a factor of 4, since CP α (2r)2 α 4r2 Collecting Power
World’s largest refracting telescope – The Yerkes 1-m telescope – University of Chicago
World’s Largest Optical Telescope One of the twin Keck telescopes – 36 mirrors cover an area 10 meters in diameter – Mauna Kea, Hawaii
One of the two Gemini telescopes. One of this telescope pair is on Mauna Kea, Hawaii; the other one is in Chile. The mirror of each telescope is about 8 meters in diameter. The yellow lines show the light path through the telescope.
Diffraction of water and light Diffraction limits the ability to observe fine details. angular resolution (arc seconds) = 0.02 * wavelength (nm)/telescope diameter (cm)
α – angular separation of objects in arc seconds λ – observed wavelength of light in nm D – diameter of telescope lens or mirror α = 0.02λ/D For D = 50 cm and λ = 500 nm (visible light): α = 0.02 * 500/50 = 0.2 arc seconds So, observing in visible light with the given telescope allows us to resolve objects that are separated by 0.2 arc seconds or more. For D = 50 cm and λ = 50 nm (ultra-violet light): α = 0.02 * 50/50 = 0.02 arc seconds So, observing in ultra-violet light with the given telescope allows us to resolve objects that are separated by 0.02 arc seconds or more. Resolution Example
Telescope Versus Interferometer Can observe 2 stars!
Jupiter Cat’s eye nebula Ring of gas around Supernova 1987 A Hourglass Nebula Images from the Hubble Disk of hot gas in core of the galaxy NGC 4261; a black hole may lie in the disk’s center