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Instruments. 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. - PowerPoint PPT Presentation
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Instruments
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.
Size refers to the size of the objective lens
The bigger the objective lens, the more light gathering power the telescope has
Refractors
http://astro.uchicago.edu/yerkes/
Yerks Observatory, U Chicago Williams Bay, WI
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
Reflector
http://d1jqu7g1y74ds1.cloudfront.net/wp-content/uploads/2008/07/reflecting.gif
http://telescopeguide.net/wp-content/uploads/2013/01/REFLECTOR-diagram.jpg
http://web.williams.edu/astronomy/Course-Pages/111/Images/reflect-tel-types.gif
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
For a telescope, why is bigger better?
Advances in Ground Based Telescopes
Ground Based Telescopes of Note
Telescope Years Important
Size
Yerks: U Chicago(Williams Bay, WI)
Built 1897 1.02 m
Hale: Mt. Wilson Institute, CA
1908 1.5 m
Hooker: Mt. Wilson Institute, CA 1917
2.5 m
Hale: Palomar, CaltecCA
1948 5.1 m
Keck I, Keck II: Mauna Kea, HI
1991 10 m
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
http://upload.wikimedia.org/wikipedia/commons/c/c0/Rear_of_Primary_Mirror_of_Keck_Telescope.jpg
This is the rear of the primary mirror assembly
Keck Telescope 10 m
http://www4.uwsp.edu/physastr/kmenning/images/keck-diagram.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
Looking beyond the visible
Published 02 April 2009The University of Waikato
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
Spitzer
http://www.spitzer.caltech.edu/mission/where_is_spitzer
Ultraviolet 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
View of the Astro-1 astronomical observation
payload in the bay of Shuttle
Columbia during the STS-35 mission of December 1990
X-Rays Electromagnetic Energy
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
Chandra X-ray Telescope
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
Why do astronomers use a variety of telescopes?
Hubble
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
Hubble
Hubble: a Cassegrain reflector Light hits the telescope's main
mirror, or primary mirror Light bounces off the primary mirror
and encounters a secondary mirror secondary mirror focuses the light
through a hole in the center of the primary mirror that leads to the telescope's science instruments
Hubble’s Instruments The Wide Field Camera 3 (WFC3) sees three
different kinds of light: near-ultraviolet, visible and near-infrared, though not simultaneously. Its resolution and field of view are much greater than that of Hubble's other instruments. WFC3 is one of Hubble's two newest instruments, and will be used to study dark energy and dark matter, the formation of individual stars and the discovery of extremely remote galaxies previously beyond Hubble's vision.
Hubble’s Instruments The Cosmic Origins Spectrograph (COS),
Hubble's other new instrument, is a spectrograph that sees exclusively in ultraviolet light. Spectrographs acts something like prisms, separating light from the cosmos into its component colors. This provides a wavelength "fingerprint" of the object being observed, which tells us about its temperature, chemical composition, density, and motion. COS will improve Hubble's ultraviolet sensitivity at least 10 times, and up to 70 times when observing extremely faint objects.
Hubble’s Instruments The Advanced Camera for Surveys (ACS)
sees visible light, and is designed to study some of the earliest activity in the universe. ACS helps map the distribution of dark matter, detects the most distant objects in the universe, searches for massive planets, and studies the evolution of clusters of galaxies. ACS partially stopped working in 2007 due to an electrical short, but was repaired during Servicing Mission 4 in May 2009.
Hubble’s Instruments The Space Telescope Imaging Spectrograph
(STIS) is a spectrograph that sees ultraviolet, visible and near-infrared light, and is known for its ability to hunt black holes. While COS works best with small sources of light, such as stars or quasars, STIS can map out larger objects like galaxies. STIS stopped working due to a technical failure on August 3, 2004, but was also repaired during Servicing Mission 4.
Hubble’s InstrumentsThe Near Infrared Camera and Multi-Object Spectrometer (NICMOS) is Hubble's heat sensor. Its sensitivity to infrared light — perceived by humans as heat — lets it observe objects hidden by interstellar dust, like stellar birth sites, and gaze into deepest space.
Hubble’s InstrumentsFinally, the Fine Guidance Sensors (FGS) are devices that lock onto "guide stars" and keep Hubble pointed in the right direction. They can be used to precisely measure the distance between stars, and their relative motions.
The future….
Webb Space Telescope The James Webb Space Telescope (sometimes called JWST) is a large,
infrared-optimized space telescope. The project is working to a 2018 launch date. Webb will find the first galaxies that formed in the early Universe, connecting the Big Bang to our own Milky Way Galaxy. Webb will peer through dusty clouds to see stars forming planetary systems, connecting the Milky Way to our own Solar System. Webb's instruments will be designed to work primarily in the infrared range of the electromagnetic spectrum, with some capability in the visible range.
Webb will have a large mirror, 6.5 meters (21.3 feet) in diameter and a sunshield the size of a tennis court. Both the mirror and sunshade won't fit onto a rocket fully open, so both will fold up and open once Webb is in outer space. Webb will reside in an orbit about 1.5 million km (1 million miles) from the Earth.
The James Webb Space Telescope was named after the NASA Administrator who crafted the Apollo program, and who was a staunch supporter of space science.
Review
What type of telescope would you want to use to observe the following:
Galactic nuclei such as black holes?
Interstellar gas and dust?Gamma Ray Telescope
Radio or Infrared Telescopes
Additional Resources
http://web.williams.edu/astronomy/Course-Pages/104/assignment.html