Concept explainers
People are often bothered when they discover that reflecting telescopes have a second mirror in the middle to bring the light out to an accessible focus where big instruments can be mounted. “Don’t you lose light?” people ask. Well, yes, you do, but there is no better alternative. You can estimate how much light is lost by such an arrangement. The primary mirror (the one at the bottom in Figure 6.6) of the Gemini North telescope is 8 m in diameter. The secondary mirror at the top is about 1 m in diameter. Use the formula for the area of a circle to estimate what fraction of the light is blocked by the secondary mirror.
Figure 6.6 Focus Arrangements for Reflecting Telescopes. Reflecting telescopes have different options for where the light is brought to a focus. With prime focus, light is detected where it comes to a focus after reflecting from the primary mirror. With Newtonian focus, light is reflected by a small secondary mirror off to one side, where it can be detected (see also Figure 6.5). Most large professional telescopes have a Cassegrain focus in which light is reflected by the secondary mirror down through a hole in the primary mirror to an observing station below the telescope.
Trending nowThis is a popular solution!
Chapter 6 Solutions
Astronomy
Additional Science Textbook Solutions
The Cosmic Perspective Fundamentals (2nd Edition)
University Physics Volume 2
Life in the Universe (4th Edition)
An Introduction to Thermal Physics
University Physics Volume 3
Physics (5th Edition)
- You are using a telescope is to resolve two distant stars as well as possible. Which of the following modifications will increase the resolution of the telescope? Question 8 options: Use a filter to filter out all but the red light. Use a filter to filter out all but the blue light. Use a lens of smaller diameter Use a lens of larger diameter None of these modifications will impact the resolution of the telescope.arrow_forwardLet's say we're considering one particular telescope. If we want to see a bigger piece of the sky, what should we do? a Point the telescope at a different part of the sky b Use an eyepiece with a longer focal length c Use an eyepiece with a shorter focal length d Each particular telescope can only show one size of "piece of the sky"arrow_forwardThe NTT telescope has a 3.58 m primary mirror and a focal ratio of f/2.2. a. Calculate the focal length of the primary mirror of the NTT telescope. b. What is the value of the plate scale of the NTT? c. Bootes is a double star system whose components are separated by 2.9". Calculate the linear separation of the images on the primary mirror focal pane of the NTT.arrow_forward
- The sun is 150,000,000 kmkm from earth; its diameter is 1,400,000 kmkm. For a science project on solar power, a student uses a 24-cmcm-diameter converging mirror with a focal length of 51 cmcm to focus sunlight onto an object. This casts an image of the sun on the object. For the most intense heat, the image of the sun should be in focus. What is the diameter of the image? Express your answer with the appropriate units.arrow_forwardA telescope is used to resolve two distant stars. By what factor will the resolution of the telescope change if the diameter of the lens is doubled? a)The resolution will increase by a factor of 4 b)The resolution will increase by a factor of 2 c)The resolution will not change, although more light will be collected. d)The resolution will decrease by a factor of 2 e)The resolution will decrease by a factor of 4 f)arrow_forwardYou have been asked to compare four proposals for telescopes to be placed in orbit above the blurring effects of the earth’s atmosphere. Rank the proposed telescopes in order of their ability to resolve small details, from best to worst. (i) A radio telescope 100 m in diameter observing at a wavelength of 21 cm; (ii) an optical telescope 2.0 m in diameter observing at a wavelength of 500 nm; (iii) an ultraviolet telescope 1.0 m in diameter observing at a wavelength of 100 nm; (iv) an infrared telescope 2.0 m in diameter observing at a wavelength of 10 mm.arrow_forward
- A Newtonian telescope has a mirror diameter of 300 mm and a focal length of 1500mm. The tube has an external diameter of 330mm and the focal plane is 40mm outside the tube.arrow_forwardDefine magnifying power of a telescope. Write its expression.A small telescope has an objective lens of focal length 150cm and an eye piece of focal length 5cm. If this telescope is used to view a 100m high tower 3km away, find the height of the final image when it is formed 25cm away from the eye piece.arrow_forwardTelescopes do more than just magnify images. In fact, if all they did was magnify images Galileo would have never seen the moons of Jupiter. What other important thing does the telescope do? a)The telescope is better at tracking movement than the naked eye is. b)The telescope is able to take disorderly rays and collimate them. c)The telescope is able to discern more colors than the naked eye can. d)The telescope is able to gather more light than the naked eye can. Kepler's design allowed him to achieve better image quality and higher magnifications than Galileo's. However, his design has a significant drawback. What is it? a) Kepler's telescope has rays intersecting each other, which creates the possibility that they will interfere with each other. b) Kepler's telescope is less able to collimate chaotic incoming light. c) Kepler's telescope collects less light. d) Kepler's image is inverted, while Galileo's is upright.arrow_forward
- The primary mirror of a telescope is 2.4 m in diameter. At what altitude will you need to pilot the telescope in order to resolve things on a 3.0 cm scale?arrow_forwardWhy does primary or objective lens of a refracting telescope should have a longer focal length?arrow_forwardWhich of these telescopes has the largest mirror, that is, the most "light gathering" capability? Palomar telescope, in California north of San Diego, with its single Pyrex mirror cast by Corning Glass. Vera Rubin telescope in Chile, soon to have the world's largest digital camera. James Webb Space Telescope, in orbit around the Sun at a Lagrange point beyond Earth. Hubble Space Telescope, oribing Earth every 90 minutesarrow_forward
- AstronomyPhysicsISBN:9781938168284Author:Andrew Fraknoi; David Morrison; Sidney C. WolffPublisher:OpenStaxPrinciples of Physics: A Calculus-Based TextPhysicsISBN:9781133104261Author:Raymond A. Serway, John W. JewettPublisher:Cengage Learning
- Foundations of Astronomy (MindTap Course List)PhysicsISBN:9781337399920Author:Michael A. Seeds, Dana BackmanPublisher:Cengage LearningStars and Galaxies (MindTap Course List)PhysicsISBN:9781337399944Author:Michael A. SeedsPublisher:Cengage Learning