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Don Peckham "The Tensegrity String Telescope"

Abstract:  String telescopes have been popular with amateur telescope builders for some time.  A string scope is similar to a truss-tube design but uses rods and tightly tied strings to support the secondary cage and to keep it rigidly positioned with respect to the primary mirror box.  Such scopes have very nice properties.  They are light, compact and easy to transport.  They have a small number of loose parts, are easy to set up, and generally maintain collimation between set-ups.  But traditional string designs also have a few limitations.  A traditional string and rod structure may require very large string tension and rod pressure to achieve needed rigidity.  One needs to make sure the mirror box is stiff enough to not warp due to high string and rod forces.  Making the mirror box stiffer also makes it heavier than one might like.  An alternative design that mitigates some of these shortcomings is a tensegrity string telescope.  In my presentation, I will describe tensegrity structures and show several variations of them.  Then, I will compare traditional and tensegrity designs and provide you with "dos and dont's" when designing a string telescope.  At the end, I will demonstrate my 3-strut and 4-strut tensegrity scopes, which I encourage you to come "handle" at the end of the meeting.  

Profile:  Don Peckham has been an RCA member for 15 years.  He ground and figured his first mirror at RCA telescope workshops in 2000, and is currently co-director of the RCA Telescope Workshop.  He has designed and built two truss tube telescopes, two "traditional" string telescopes and two tensegrity string telescopes.  He created and maintains the "String Telescope Concepts" website.  He is also an avid banjo player and is the proud owner and operator of several banjos, including some wonderful vintage instruments.

Here are links to his websites:

http://dbpeckham.com/Telescope/String/StringScope.htm

http://dbpeckham.com/Telescope/String/TensegrityString12.5.htm