Why use a telescope? • Light gathering: telescopes collect more light than the human eye can capture on its own • Magnification
Refractor Telescopes http://www.bro.lsu.edu/telescope/Classroom/2.How%20Telescopes%20Work/Refracting.gif
Refraction - the bending of light due to the fact it slows down while going through a dense medium.
Refractors • Size refers to the size of the objective lens • The bigger the objective lens, the more light gathering power the telescope has
Yerks Observatory, U Chicago Williams Bay, WI http://astro.uchicago.edu/yerkes/
Yerkes Observatory • Largest refractor • 40 inch objective (102 cm) http://astro.uchicago.edu/vtour/40inch/40inchtour.jpg
Magnification The focal length of the objective lens Magnification = ------------------------------------------------ The focal length of the eyepiece How can you change the magnification without changing the light collecting power?
Warm up: • Which part of a refractor telescope is light gathering? • What does the magnification?
Amazing History of the Telescope • ESA: Eyes on the Skies Chapter 1 • http://www.youtube.com/watch?v=A68Hta5RxWg
Refractor- Advantages • After initial alignment, refractor optics are more resistant to misalignment • The glass surfaces are sealed inside the tube and rarely need cleaning. • The sealing also minimizes affects from air currents, providing steadier sharper images. http://space.about.com/cs/telescopes/a/scopebasics.htm
Disadvantages • possible distortions of the lenses. • lenses need edge supported, this limits the size of any refractor • Lenses can “sag” over time • Chromatic aberration
Chromatic Aberration • only 1 frequency focuses at a time because of dispersion • each frequency slows a different amount in glass http://www.astronomynotes.com/telescop/s2.htm
Chromatic Aberration http://www.astronomynotes.com/telescop/s2.htm
Mt. Wilson Hooker reflector • 100 inch mirror (2.5 m) • Biggest telescope between 1917 - 1948 http://www.mtwilson.edu/vir/100/
Palomar Observatory (Cal Tec) http://www.astro.caltech.edu/palomar/images/speed.limit.jpg
Palomar Observatory • California Institute of Technology • North of San Diego, CA • 5 telescopes
Hale telescope http://www.astro.caltech.edu/palomar/
Reflectors- advantages • Reflectors do not suffer from chromatic aberration (inability to focus all colors). http://space.about.com/cs/telescopes/a/scopebasics.htm
Advantages (cont’d) • Mirrors are easier to build without defects than lenses, since only one side of a mirror is used. • because the support for a mirror is from the back, very large mirrors can be built, making larger scopes.
Reflectors- Disadvantages • The disadvantages include easiness of misalignment and need for frequent cleaning. http://space.about.com/cs/telescopes/a/scopebasics.htm
Keck I & Keck II • 300 tons each http://amazing-space.stsci.edu/resources/explorations/groundup/lesson/scopes/keck/graphics/map_keck.jpg http://www.ucolick.org/~kibrick/remoteobs/jtechs2001/distantkecks_5B1_5D.jpg
This is the rear of the primary mirror assembly http://upload.wikimedia.org/wikipedia/commons/c/c0/Rear_of_Primary_Mirror_of_Keck_Telescope.jpg
Interferometry • Using multiple small telescopes to form an image effectively simulating a much larger telescope • http://planetquest.jpl.nasa.gov/technology/technology_index.cfm
Problems with Ground Telescopes • "atmospheric distortion" is the reason that the stars seem to twinkle when you look up at the sky • atmosphere partially blocks or absorbs certain wavelengths of radiation, like ultraviolet, gamma- and X-rays, before they can reach Earth
Infrared Energy • heat energy • Observed in dry, high altitude locations or space • Observation of: • galactic regions cloaked by dust • studies of molecular gases. NASA Infrared Telescope Facility- Mauna Kea, Hawaii
Ultraviolet View of the Astro-1 astronomical observation payload in the bay of Shuttle Columbia during the STS-35 mission of December 1990 • absorbed by atmospheric ozone • observed from very high altitude or space • best suited to the study of thermal radiation and spectral emission lines from hot blue stars that are very bright in this wave band
X-Rays Electromagnetic Energy Chandra X-ray Telescope • absorbed by atmosphere • Observed by high altitude balloons, rockets, or from space Notable X-ray sources include: • X-ray binaries • pulsars • supernova remnants • active galactic nuclei
Fermi X Ray Telescope Fermi Bubbles - found by the Fermi telescope in 2010 - extend 20,000 light-years above and below our Milky Way galaxy.
Fermi X Ray Telescope • http://earthsky.org/space/mysterious-objects-at-edge-of-electromagnetic-spectrum Fermi Bubbles - found by the Fermi telescope in 2010 - extend 20,000 light-years above and below our Milky Way galaxy.
Gamma ray Electromagnetic Energy • observed in space or indirectly with special ground based telescopes Steady gamma-ray emitters include: • Pulsars • neutron stars • black hole candidates such as active galactic nuclei Compton Gamma-ray Observatory launched on the Space Shuttle Atlantis, mission STS-37, on 5 April 1991 and operated until its de-orbit on 4 June 2000
Nat Geo- Hubble • Read Hubble Space Telescope-Eyes in the Sky • Complete the article/text analysis document
DATA PATH BEFORE IMAGE IS CREATED HOW IMAGES ARE MADE!! http://hubblesite.org/gallery/behind_the_pictures/
The new image (right) was taken with the second generation Wide Field and Planetary Camera (WFPC2), which was installed during the STS-61 Hubble Servicing Mission. The picture beautifully demonstrates that the corrective optics incorporated within WFPC2 compensate fully for Hubble's near-sightedness. The new camera will allow Hubble to probe the universe with unprecedented clarity and sensitivity. The picture clearly shows faint structure as small as 30 light-years across in a galaxy tens of millions of light-years away. An Early Release Observation Release / An American Astronomical Society Meeting Release January 13, 1994
Hubble Telescope • 353 miles (569 km) above the surface of Earth • Every 97 minutes, Hubble completes a spin around Earth • moving at the speed of about five miles per second (8 km per second) — fast enough to travel across the United States in about 10 minutes