Pictures of my String Telescope. 16" f/4.5 Dobsonian  

The main reason I chose to use string was not for lower weight, but for ease of setup.  Just hook the strings onto the secondary then turn the three Aluminum poles to tension.

The secondary cage is held in place by three pairs of strings.   Because they must be in tension, each of the pairs of strings are supported by an aluminum tube.  The tube and its associated strings connect to a solid piece of Aluminum so there is no stress on the wooden rings of the secondary cage.  The top of the tube has a threaded insert with a rectangular-headed bolt.  The bolt fits into a matching hole in a small piece of 1/2" thick Aluminum stock which is mounted to the secondary ring.  As you turn the Aluminum tube the bolt unscrews causing tension on the string.

The string I chose was a bowstring called 450plus, it is a blend of Vectran and Spectra and has incredibly low stretch.  Each string is comprised of 20 strands.  The string is sheathed in nylon webbing.  I left the webbing bunched up a bit in an attempt to reduce vibration.  I have noticed no vibration problems during observing.

Does the string stretch?  When pointing the scope from vertical to horizontal, a laser collimator's spot on the primary does not perceptibly move. 

Pictures of this scope in action:

At the Table Mountain Star Party where it won best Dobsonian award.

At the Oregon Star Party where it was featured in the telescope walkabout (with reworked altitude bearings).

	Once the strings are adjusted for collimation, they should not normally have to be adjusted again.
	Aluminum block on secondary cage used as common mounting point.

Matt Vartanian
Portland, OR

Questions?   Email me

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