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Transcript
A reflecting telescope (also called a reflector reflector) is an optical telescope which uses a single or combination of curved mirrors that reflect light and form an image. The reflecting telescope was invented in the 17th century as an alternative to the refracting telescope.. The reflecting telescope uses very large diameter objectives so that more light can be collected and objects appear clearer. Almost ost all of the major telescopes used in astronomy research are reflectors. Reflecting telescopes come in many design variations and may employ extra optical elements to improve image quali quality ty or place the image in a mechanically advantageous position. Since reflecting telescopes use mirrors,, the design is sometimes referred to as a "catoptric" telescope. The advantages of optical telescopes like the reflecting telescope are that they are easy to purchase, easy to use, and that the images are easy to understand. Reflecting telescopes are ideal for galaxy hunting hunti and finding other faint, far away objects. All optical telescopes like the reflecting telescope have a few disadvantages. Like the refracting telescope, colors appear in the image that are not really there. (chromatic aberration) The large diameter objectives o in the reflecting telescopes minimize this problem. Additionally, optical telescopes will only detect visible light. The Newtonian Reflecting telescope was the first successful reflecting telescope, completed by Isaac Newton in 1668. It usually has a curved primary mirror, and a flat secondary mirror reflects the light to a focal plane lane at the side of the top of the telescope tube. It is one of the simplest and least expensive designs for a given size of primary, and is popular with amateur telescope makers as a home-build build project. A refracting or refractor telescope is a type of optical telescope that uses a lens as its objective to form an image (also referred to a dioptric telescope telescope). ). The refracting telescope design was originally used in spy glasses and astronomical telescopes but is also used for long telephoto camera lenses. All refracting telescopes use the same principles. The combination of an objective lens 1 and some type of eyepiece 2 is used to gather more light than the human eye could collect on its own, focus it 5,, and present the viewer with a brighter, clearer, and magnified virtual image 6. The main disadvantage of refracting efracting telescopes is that they are known for incorrectly bending light and creating false colors, called a chromatic aberration. For example, a refracting telescope may put a false purple halo around the moon. In very large telescopes that have large lenses, there is also a problem of lens sagging, a result of gravity deforming glass.. Since a lens can only be held in place by its edge, the center of a large lens sags due to gravity, distorting image it produces. The largest practical lens size in a refracting telescope is around 1 meter. Another disadvantage of refracting telescopes is that the image can be distorted by light in the Earth’s atmosphere. For this reason, refracting telescopes are place at the tops This is an optical telescope image of the Milky Way Galaxy from space. This is a side view. of mountains and will have large domes to shield the telescope telesc from light in the atmosphere. Finally, refracting telescopes will only detect visible light. Black holes do not give off visible light and therefore cannot be detected by optical telescopes. Despite its limitations, it is still a good beginning tele telescope, and it is ideal for observing details of objects within the solar system like craters on the moon, or details of the planets. The Griffith Observatory in Los Angeles is an excellent example of a refracting telescope. Griffith Observatory A radio telescope is a form of directional radio antenna used in radio astronomy.. The same types of antennas are also used in tracking and collecting data from satellites and space probes. Radio telescopes will detect radio waves, the same waves that you listen to on the radio radio, and convert them to an image. Radio telescopes are typically large parabolic ("dish") antennas used alone or in an array with other telescopes. They are excellent telescopes forr viewing rath rather er cool objects in the universe or objects that do not give off visible light. Radio observatories are preferentially located far from major centers of population to avoid electromagnetic interference (EMI) from radio, TV, radar,, and other EMI emitting devices. This is similar to the locating of optical telescopes to avoid light pollution, pollution with the difference being that radio observatories are often placed in valleys or cones of volcanoes (like the Arecibo Radio Telescope in San Juan, Puerto Rico) to further shield them from EMI as opposed to clear air mountain tops for optical observatories. VLA or Very Large Array located outside of Socorro, New Mexico. The main advantage of radio telescopes is that they “see” other types of light that are not visible. They operate in the radio frequency (invisible) portion of the electromagnetic spectrum where they can detect and collect data on radio sources. Common radio sources include the centers of galaxies, cooler Background Radiation of the Universe and emissions from stars. More famously (in the he movie Contact), this type of telescope is used by SETI to search for extraterrestrial life. You can help them in their search by going to http://setiathome.berkeley.edu/ . The main disadvantages to radio telescopes elescopes are that they are expensive because you must have many of them is an isolated location. Scientists must Images of Galaxy M87 from Radio Telescope Arrays A VLA and VBLA have extensive training on how to use the arrays as well as to understand the images. A space observatory is any instrument in outer space which is used for observation of distant planets, galaxies, and other outer space objects. This category is distinct from other observatories located in space that are pointe pointed d toward the earth for the purpose of scientific research, research spying or weather forecasting forecasting. Many space observatories have already completed their missions, while others continue operating, and still others are planned for the future. Space observatories are important because they can not only make observations in the visible range, like the Hubbl Hubblee Space Telescope, but they allow us to see light outside of visible range range, such as x-rays.. One great example would be the SOHO, the Solar and Heliospheric Observatory,, which allows us to study the Sun un in Ultraviolet, Radio and X Rays. These types of observatories es are especially important because the atmosphere blocks some types of light from hitting the surface of the Earth, which keeps us from studying that light light. For example, X-ray astronomy is nearly impossible when done from the Earth, and has reached its current importance in astronomy only due to orbiting X X-ray telescopes such as the Chandra handra observatory and the XMM-Newton observatory. Infrared and ultraviolet light waves are also greatly blocked by our atmosphere, and we must go to space to study these types of light from stars. X-ray ray image of Casseopeia II Constellation of Stars from Space Observatory Chandra The main disadvantages of space observatories are that they are expensive. Space observatories must be launched unched into space and require many years of training to use. If something goes wrong with the telescope, the problem must be detected on Earth, a team of astronauts must be trained on how to fix the problem, and then the crew must be launched into space. X-ray ray and UV light images can be very difficult to understand.