Oregon Star Party 2007 Telescope Walkabout

Mel Bartels, August 2007, images by Greg Babcock


Each year we hold a telescope walkabout at the Oregon Star Party.  Telescope builders share their experiences making telescopes.  People walkabout the telescopes to enjoy the telescope making experiences and to garner ideas for their own telescopes.

This year's themes are string scopes, travel scopes and gigantic scopes.

Craig Combes' 16 inch ultra-lite/compact with carbon fiber tubes.  Craig traveled with his scope from Hawaii to New Zealand, storing the telescope in the overhead bin.  The entire package weighs 27 pounds with 0.9 inch thick quartz primary mirror.  The carbon fiber parts obtained from Boeing Surplus are glued with Gorilla glue.


   

Howard Banich's 13 inch string travel scope is built from Alucobond, an inexpensive to carbon fiber graphic.  Alucobond can be obtained from Aurora Precision in Portland Oregon and cuts like plywood using same tools.  Howard reports that the strings are very stress on the mirror box which must be made very stiff.  Howard set the azimuth pivot back in the flex rocker so that the scope that is balanced with springs does not topple over when aimed low at the horizon.  The truss tubes are tent poles from REI.


Tom Conlin's 16 inch ball scope features a loosely coupled ball such that the optical tube assembly can be pulled out from the ball by lifting it up.  The 3 strings support the truss tubes.  The1/2 inch thick polyethylene ball cost $80 from New Jersey.  Tom smoothed the ball by a router that had nuts attached to form the proper spheroidal radius, the router being moved across the ball until the ball became perfectly round and smooth.  Optical alignment (collimation) is handed by a translating secondary (no primary mirror cell adjustments).  History of the building of the scope can be found at flickr.com, searching for 'luceal'.


Dan Bakken's 41 inch f/3.9 scope is a much lighter string version of the original telescope.  The mirror is glued to the cell with RTV and Dan reports much better images than the previous 27 point support with sling.  Dan also reports that the new version is much more wind resistant.






Ken Lulay's 12 inch string scope without upper ring features a minimal set of tubes and strings.  The strings loop over the spider plate constraining the plate's position from rotating on its long axis, resisting torque caused by the weight of the secondary mirror.  The entire scope fits into a small box and weighs 30 pounds.  The focuser is homemade.  An innovative bent baffle keeps light from flooding the eyepiece field of view.


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