![]() (c) Infrared radiation: here, we mainly see the glowing dust in this region. The bright, hot stars in Orion are still seen in this image, but so are many other objects located at very different distances, including other stars, star corpses, and galaxies at the edge of the observable universe. The colors are artificial, changing from yellow to white to blue with increasing energy of the X-rays. (b) X-rays: here, the view emphasizes the point-like X-ray sources nearby. (a) Visible light: this shows part of the Orion region as the human eye sees it, with dotted lines added to show the figure of the mythical hunter, Orion. The same part of the sky looks different when observed with instruments that are sensitive to different bands of the spectrum. Third, we need some type of detector, a device that senses the radiation in the wavelength regions we have chosen and permanently records the observations.įigure 6.2 Orion Region at Different Wavelengths. But at other times, we want to see individual spectral lines to determine what an object is made of, or to measure its speed (as explained in the Radiation and Spectra chapter). For example, we might simply want to separate blue light from red light so that we can determine the temperature of a star. Second, there is an instrument attached to the telescope that sorts the incoming radiation by wavelength. Just as you can catch more rain with a garbage can than with a coffee cup, large telescopes gather much more light than your eye can. First, there is a telescope, which serves as a “bucket” for collecting visible light (or radiation at other wavelengths, as shown in ( Figure 6.2). There are three basic components of a modern system for measuring radiation from astronomical sources. Describe the two basic types of visible-light telescopes and how they form images.Describe the main functions of a telescope.Describe the three basic components of a modern system for measuring astronomical sources.One can get special lenses that have a special coating to reduce the amount of chromatic aberration but they are expensive.By the end of this section, you will be able to: The result of this is that the edges of the image are blurred and coloured like fuzzy rainbows. This is how a prism splits white light into the visible spectrum. Smaller wavelengths refract more than longer wavelengths. Different wavelengths of light refract by different amounts. (eyepieces with smaller focal lengths are more powerful as they need to bend the light more). Less powerful to locate the star and more powerful to observe it closely. When you want to observe a star you will often switch eyepieces. You don’t always want an incredibly high magnification, e.g. Star gazers usually have a selection of eyepieces at hand. a refracting telescope has an objective of focal length 70cm and eyepiece 5cm. The magnification of a refracting telescope is equal to the focal length of the objective divided by the focal length of the eyepiece.Į.g. The magnification of a telescope or any optical instrument is how much bigger the image is compared with the object. We can represent this using a ray diagram which shows the path of imaginary rays of light passing through the telescope.įrom the diagram above we can see that the distance between the lenses is the sum of the focal lengths of the two lenses. Basically the objective lens produces an image of a distant object at its focus and the eyepiece lens magnifies this image. a star or planet.Ī simple refracting telescope consists of two lenses, the Objective and the eyepiece. A refracting telescope uses a combination of lenses to produce an image of a distant object, e.g. ![]() A lens is a piece of glass designed to bend the light that passes through it in such a way that an image may be produced. When a wave such as light passes from one medium to another at an angle it changes direction. ![]() In this article we will focus on refracting telescopes, although there are other types of telescopes such as reflecting. Telescopes also help us see many more stars than we can ever could with the naked eye. This includes the detail on the surfaces of close objects like the Moon and the planets. ![]() Since the invention of telescopes astronomers have been able to see a considerable amount when gazing into the vastness of space. ![]()
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