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Astronomy Links Amateur Telescope Making Here is some advice on making your own telescope For a good explanation of telescope basics go here or to Celestron International Tips for
Building a Newtonian Telescope The easiest telescope design for the amateur to make is the Newtonian. This basically consists of a large primary mirror for collecting the image at one end and a small secondary mirror at the other end that directs the image to the eyepiece for viewing. The primary mirror is held in place by an adjustable frame attached to the telescope tube called the primary cell. The secondary is held in place by another adjustable frame called the spider. A hole is cut into the telescope tube above the secondary for a focuser. The focuser holds the eyepiece, which magnifies the image. Most amateurs use high quality Plossl eyepieces. There are three types of focuser, rack and pinion, crayford and helical focusers, the choice depends on what the telescope will be used for. The rack and pinion is suitable for general use. The rack and pinion allow the greatest amount of adjustment and work well with all types of telescopes, but does not allow fine adjustment or support heavy weights. There is usually some image shift involved with rack and pinion focusers, due to the coarse nature of their adjustment. This can be overcome by using an additional helical focuser for fine adjustment. The crayford is the strongest, most stable focuser for mounting cameras and other equipment. The crayford is very stable for attaching cameras and other equipment on larger telescopes. The helical focuser allows the finest focus adjustment with zero image shift and is also very stable for attaching cameras. It is widely used to replace rack and pinion focusers on SCT telescopes to eliminate image shift. The best choice is probably a crayford type focuser, providing very good adjustment capability with the ability to support heavy loads for additional equipment. There are two types of mount for the telescope, the Equatorial mount has right ascension and declination scales for keeping track of the telescopes position and can also be adjusted to track the stars as they move. This mount is usually purchased; however there is another type of mount called the Dobsonian which can easily be made from plywood. Most amateurs will start with a Dobsonian mount. Materials The telescope tube is usually made from a spiral wound cardboard tube called a sonotube. You can also make your own tube from metal but generally, the best option is to purchase a sonotube from one of the telescope and equipment suppliers. If you are building a telescope for the first time you will want to buy all the pieces readymade and assemble them into the final product. There are two types of mirrors, soda lime glass or Pyrex. The only difference between soda lime glass and Pyrex during use is that glass takes longer to adjust to temperature changes, the image quality is the same for both. The mirrors need to be ground to a precision of 1/8 wave or less to produce a high quality image, avoid mirrors that have an accuracy of 1/6 wave. When buying mirrors buy the primary and secondary at the same time and specify a mirror set. Mirror holders, focusers and eyepieces are pretty much standard, just make sure you buy the correct ones. The mirror holders should be adjustable and must be the correct size to fit your mirrors and tube. Eyepieces for telescopes have either 1 1/4" or 2" diameters. The larger telescopes, above 8" should have 2" focusers and eyepieces. Again, most amateurs use high quality Plossl eyepieces. To find suppliers where you can purchase all the parts look in our Space and Planetary Science links section. List of Astronomy Software you might find useful Tips When Assembling Your Scope If any of the mirrors attract dust or grease leave them until the scope is assembled. After the scope is assembled use a soft cloth and lightly clean the grease and dust. Use acetone or isopropyl alcohol as the cleaning agent. If there is only dust, remove the dust with a clean soft camera brush. Minor dust can be left as it will not affect the image much and is unavoidable once you are using the scope unless you have an airless vacuum chamber!!. 1. Drill the focuser hole in
the center of the tube and slightly larger than the focuser A homemade motorized scotch mount is here.  email Text and Images Copyright ©2004-2010 by Rob Kanen |
