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1395Re: [delmarvastargazers] Apodising Screen details

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  • Teresa T. Young
    Jul 1, 2003
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      James,
          The book says to do the following -

          You will be using two measurements - the diameter of the outside of your telescope and the diameter of you actual mirror.  I did hear someone say that this screen does not seem to work well on scopes smaller than eight inches. If you use a refractor, you will want to make the hole diameters 52%, 76% and 88% the size of the objective.

          Using ordinary wire mesh (same used for screens in windows), cut two disks equal in diameter to the outside diameter of your telescope tube.  Cut the third disk similarly, but leave three tabs spaced 120 degrees apart (You'll use these to hold the screen onto the end of your telescope).

          You will be cutting one hole per disk and you will want the holes to be concentric when you stack the disks together. Now to cutting holes, for the third disk with the tabs, cut a hole in the center that disk that is equal to 55% of  the diameter of your telescope mirror.  In the second disk, cut a hole that is 78% the diameter of your mirror. In the first disk, cut a hole that is 90% the diameter of the mirror.

          To assemble, take the second 78% disk and lay it on the third 55% disk so that the mesh is at a 30 degree angle. Then take the first 90% disk and lay it on the others at a thirty degree angle to the second 78% disk's mesh.

          Staple the screens together, bend the flaps at a 90 degree angle towards the side that the other disks are attached. The flaps will hold the disk in place when you place it over the end of the telescope. The wire may be sharp so be sure to watch your hands and not let it get too close to anything it might scratch.
       

          Hopefully that will help James! Let me know. I think I will try to build one later next week.

      Best,

      Teri

      James T. Morgan wrote:
      Teresa, can you provide some details for making this
      screen?




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