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Learning objectives

By the end of this section, you will be able to:

  • Recognize the largest visible-light and infrared telescopes in operation today
  • Discuss the factors relevant to choosing an appropriate telescope site
  • Define the technique of adaptive optics and describe the effects of the atmosphere on astronomical observations

Since Newton’s time, when the sizes of the mirrors in telescopes were measured in inches, reflecting telescopes have grown ever larger. In 1948, US astronomers built a telescope with a 5-meter (200-inch) diameter mirror on Palomar Mountain in Southern California. It remained the largest visible-light telescope in the world for several decades. The giants of today, however, have primary mirrors (the largest mirrors in the telescope) that are 8- to 10-meters in diameter, and larger ones are being built ( [link] ).

Large telescope mirror.

Photograph of one of the 8-meter concave primary mirrors of the European Space Agency’s Very Large Telescope array in Chile.
This image shows one of the primary mirrors of the European Southern Observatory’s Very Large Telescope, named Yepun, just after it was recoated with aluminum. The mirror is a little over 8 meters in diameter. (credit: ESO/G. Huedepohl)

Modern visible-light and infrared telescopes

The decades starting in 1990 saw telescope building around the globe grow at an unprecedented rate. (See [link] , which also includes websites for each telescope in case you want to visit or learn more about them.) Technological advancements had finally made it possible to build telescopes significantly larger than the 5-meter telescope at Palomar at a reasonable cost. New technologies have also been designed to work well in the infrared, and not just visible, wavelengths.

Large Single-Dish Visible-Light and Infrared Telescopes
Aperture (m) Telescope Name Location Status Website
39 European Extremely Large Telescope (E-ELT) Cerro Armazonas, Chile First light 2025 (estimated) www.eso.org/sci/facilities/eelt
30 Thirty-Meter Telescope (TMT) Mauna Kea, HI First light 2025 (estimated) www.tmt.org
24.5 Giant Magellan Telescope (GMT) Las Campanas Observatory, Chile First light 2025 (estimated) www.gmto.org
11.1 × 9.9 Southern African Large Telescope (SALT) Sutherland, South Africa 2005 www.salt.ac.za
10.4 Gran Telescopio Canarias (GTC) La Palma, Canary Islands First light 2007 http://www.gtc.iac.es
10.0 Keck I and II (two telescopes) Mauna Kea, HI Completed 1993–96 www.keckobservatory.org
9.1 Hobby–Eberly Telescope (HET) Mount Locke, TX Completed 1997 www.as.utexas.edu/mcdonald/het
8.4 Large Binocular Telescope (LBT) (two telescopes) Mount Graham, AZ First light 2004 www.lbto.org
8.4 Large Synoptic Survey Telescope (LSST) The Cerro Pachón, Chile First light 2021 www.lsst.org
8.3 Subaru Telescope Mauna Kea, HI First light 1998 www.naoj.org
8.2 Very Large Telescope (VLT) Cerro Paranal, Chile All four telescopes completed 2000 www.eso.org/public/teles-instr/paranal
8.1 Gemini North and Gemini South Mauna Kea, HI (North) and Cerro Pachón, Chile (South) First light 1999 (North), First light 2000 (South) www.gemini.edu
6.5 Magellan Telescopes (two telescopes: Baade and Landon Clay) Las Campanas, Chile First light 2000 and 2002 obs.carnegiescience.edu/Magellan
6.5 Multi-Mirror Telescope (MMT) Mount Hopkins, AZ Completed 1979 www.mmto.org
6.0 Big Telescope Altazimuth (BTA-6) Mount Pastukhov, Russia Completed 1976 w0.sao.ru/Doc-en/Telescopes/bta/descrip.html
5.1 Hale Telescope Mount Palomar, CA Completed 1948 www.astro.caltech.edu/palomar/about/telescopes/hale.html

Questions & Answers

What is inflation
Bright Reply
a general and ongoing rise in the level of prices in an economy
AI-Robot
What are the factors that affect demand for a commodity
Florence Reply
price
Kenu
differentiate between demand and supply giving examples
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differentiated between demand and supply using examples
Lambiv
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Lambiv
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Eliyee
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Eliyee
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WARKISA
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Lambiv
multiple choice question
Aster Reply
appreciation
Eliyee
explain perfect market
Lindiwe Reply
In economics, a perfect market refers to a theoretical construct where all participants have perfect information, goods are homogenous, there are no barriers to entry or exit, and prices are determined solely by supply and demand. It's an idealized model used for analysis,
Ezea
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Shukri Reply
other things being equal
AI-Robot
When MP₁ becomes negative, TP start to decline. Extuples Suppose that the short-run production function of certain cut-flower firm is given by: Q=4KL-0.6K2 - 0.112 • Where is quantity of cut flower produced, I is labour input and K is fixed capital input (K-5). Determine the average product of lab
Kelo
Extuples Suppose that the short-run production function of certain cut-flower firm is given by: Q=4KL-0.6K2 - 0.112 • Where is quantity of cut flower produced, I is labour input and K is fixed capital input (K-5). Determine the average product of labour (APL) and marginal product of labour (MPL)
Kelo
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Shukri
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Shukri
what is monopoly mean?
Habtamu Reply
What is different between quantity demand and demand?
Shukri Reply
Quantity demanded refers to the specific amount of a good or service that consumers are willing and able to purchase at a give price and within a specific time period. Demand, on the other hand, is a broader concept that encompasses the entire relationship between price and quantity demanded
Ezea
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Economic growth as an increase in the production and consumption of goods and services within an economy.but Economic development as a broader concept that encompasses not only economic growth but also social & human well being.
Shukri
production function means
Jabir
What do you think is more important to focus on when considering inequality ?
Abdisa Reply
any question about economics?
Awais Reply
sir...I just want to ask one question... Define the term contract curve? if you are free please help me to find this answer 🙏
Asui
it is a curve that we get after connecting the pareto optimal combinations of two consumers after their mutually beneficial trade offs
Awais
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Asui
In economics, the contract curve refers to the set of points in an Edgeworth box diagram where both parties involved in a trade cannot be made better off without making one of them worse off. It represents the Pareto efficient allocations of goods between two individuals or entities, where neither p
Cornelius
In economics, the contract curve refers to the set of points in an Edgeworth box diagram where both parties involved in a trade cannot be made better off without making one of them worse off. It represents the Pareto efficient allocations of goods between two individuals or entities,
Cornelius
Suppose a consumer consuming two commodities X and Y has The following utility function u=X0.4 Y0.6. If the price of the X and Y are 2 and 3 respectively and income Constraint is birr 50. A,Calculate quantities of x and y which maximize utility. B,Calculate value of Lagrange multiplier. C,Calculate quantities of X and Y consumed with a given price. D,alculate optimum level of output .
Feyisa Reply
Answer
Feyisa
c
Jabir
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Source:  OpenStax, Astronomy. OpenStax CNX. Apr 12, 2017 Download for free at http://cnx.org/content/col11992/1.13
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