Oregon Star Party 2007
Mel Bartels, August 2007,
images by Greg Babcock
Each year we hold a telescope walkabout at the Oregon Star
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
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.
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.
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
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'.
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
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.