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如何建立一个天文望远镜

2018-1-30 20:17| 发布者: dymodel| 查看: 925| 评论: 0|原作者: ship

摘要: 如何建立一个天文望远镜 INTRODUCTIONI describe below how to construct two telescopes. The first one is simpler to build, but is important for understanding the solutions adopted in the second one, w ...
如何建立一个天文望远镜

INTRODUCTIONI describe below how to construct two telescopes. The first one is simpler to build, but is important for understanding the solutions adopted in the second one, which is perfected and optimized for astronomical observations.THE FIRST TELESCOPEAs I said, you can build this first simple instrument without difficulty while allowing you to learn the structure and operation of telescopes in general. Although it is simple, it can reveal the craters of the Moon and the satellites of Jupiter. It is also very useful for demonstrating lens aberrations. You really need to build this telescope as a necessary step towards understanding the solutions employed in the second and improved telescope model. In the section "From Lenses to Optical Instruments", you saw how a telescope works; here I simply remind you that the objective lens produces an image of the object observed, and this image is magnified by the eyepiece.tele_02.gifFigures 2 and 3 show our first telescope, which is made using easy-to-find materials. The components of this instruments are:1 - ring to secure the eyepiece lens from behind2 - ring for centering the eyepiece lens3 - eyepiece: lens with focal length of 20-50 mm. You can buy one in an optical or photographic shop, or you can get one free by using the lens of a disposable camera.4 - ring to secure the eyepiece lens from the front5 - a cardboard tube for the eyepiece. You can use the tube from a roll of plastic food wrap or paper towels. You can also use short sections of this tube to make rings 1, 2, and 4 which you need to hold the eyepiece lens in place6 - coupling between the eyepiece tube and the main tube. This is a hollow cylinder with an outer diameter that fits snugly into the end of the main tube and an inner diameter that provides a snug but movable fit to the outside of the eyepiece tube. You can make the coupling using several plywood disks glued together or using a polystyrene cylinder with a hole bored through it. If you use polystyrene, you will need to add an opaque covering at each end.7 - main tube. Use a cardboard or plastic tube about as long as the focal length of the objective lens and with an outside diameter of 50-60 mm about. Suitable sources include map mailing tubes and core tubes for carpets, drawing paper, or wrapping paper.8 - objective lens. You can use a common eyeglass lens with a focal length of 500-1000 mm. You can buy it in a optical shop. Ask the optician to reduce the lens diameter in order to fit it precisely into the tube cap9 - diaphragm. Cut it from a black card, then open a hole of about 15 mm in diameter in the center of the disk10 - Cap of the tube. If you buy a tube for drawing sheets, you should have a cap which will be useful for retaining the objective and the diaphragm. Otherwise, you can made it with a disk of cardboard. Make a series of radial cuts around the edge of the disk to make a set of tabs, Moisten the tabs; then place the tube cap on one end of the principal tube and bend the tabs around the outside of the tube. Glue the tabs together where they overlap, but be careful not to glue the cap to the principal tube yet. When the glue is dry, slip the cap off and cut in the cap a hole a few mm less in diameter than the outside diameter of principal tube.


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