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 Instruments

The 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 Instruments

Finally, 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