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The upper tube assembly is based on more conventional truss tube designs. Randall Wehler used a pair of closet dowels and a very simple system of wood, clamps and a photographic mount to mount the eyepiece and secondary. I wanted something a bit more elegant and I was concerned about portability issues as well as diffraction spikes.
The truss tubes came from Texas Towers and the curved three-vane spider was supplied by 1800Destiny.com. The focuser is a great, lightweight, low-profile helical focuser from KineOptics. The secondary mirror (2.5" minor axis diagonal) was also purchased from 1800Destiny.com I experimented with several bases and this was ultimately, the most difficult part of the project and the last to finally complete. My first base was a plywood round with a hole hand cut with a jig saw. Because the hole was not perfectly round, I never had the smooth movements I knew were possible with this design. I then tried a base made of a pine round with a 6" landscape grate attached to the top. This provided very smooth movements but the small hole made for a higher center of gravity and I had many balance problems. I eventually went back to the first base and epoxied in an 8" stainless steel mixing bowl into my original 7 1/2" hand cut hole. This provided the ideal movement that was needed. The final picture is the scope ready for transport. The whole scope is extremely compact, although the bowl is on the heavy side when it comes to loading it in the back seat. |
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