Oregon Star Party 2008 Telescope Walkabout

Mel Bartels, August 2008

images by Greg Babcock, Howard Banich, Mark Thorson

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.

Here's a typical scene: Q&A on one of the walkabout telescopes.

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

We start with Chuck Dethloff's 16 inch f/4 (Swayze mirror).  This scope features a lightweight double ring upper cage; eyepiece shade and a low height box.  The batteries are attached below the mirror mount in an unique manner, which results in a downward shift of the center of gravity by 2.5 inches.  Chuck designs his scopes for superb responsiveness when hand pushing it for finding and high power tracking.  The upper cage uses ABS plastic, an improvement over the popular Kydex, which can deform in the hot sun.  The overall weight of the scope is 100 pounds.  Finish is Boat Koat UV varnish, 5 coats sprayed on and sanded.

Next we stepped over to Steve Swayze's 18 inch f/3.5.  It's a Coulter reclamation project with veneered tube end rings, a Swayze trademark.  Its remarkable that one has to stoop to look through the eyepiece when the scope is pointed vertically.  This is definitely no-ladder territory.  The views through the eyepiece at night were stunning, particularly with the 8mm Ethos and the bino viewer.

Next is Dave Nemo's 20 inch string scope.  Dave found the mirror at a garage sale... get this... for $100.  Dave first built an 8 inch prototype to understand the principles and work through iteration #1.  Dave built from wood because he knows wood; the scope was finished in eight weeks in time for OSP.  He used common materials that were easily available.  Dave was inspired by the other string scope builders.

We motored on over to Greg Babcock's 12 inch f/5 traveller, inspired by Greg's earlier 10 inch traveler and Albert Highne's telescope design.  The lid becomes the ground board.  The truss poles slide into interior connectors.  The scope started as a commercial 12 inch dob, purchased used.  Greg used Baltic birch throughout, with the total weight of the scope pegged at 40 pounds.  Greg's 12 inch traveller is the scope on the left of the image immediately below.

Dave Powell's 12 inch f/6 string scope, named "Beautiful Blue", is an all aluminum scope.  All poles are interchangeable.  Dave uses ball bearings for very smooth motion, and uses the 3 vane spider design that Greg Babcock first used on his 18 inch scope back in the late 1990's (http://www.synrgistic.com/astro/building.htm) The aluminum is water jet cut, including the 'stars'.  Dave's is the scope on the right of the image immediately below.

It's an interesting comparison of purpose and technique for the identical aperture of 12 inches.

David Martin's 16 inch f/4.5 'Pegasus' dob saw first light the night before.  (This is a time honored tradition at the Oregon Star Party: many of us have labored long days and nights immediately preceeding the star party, with first light the first night of the star party).   The mirror box fits under his bed (away from cats and kids!).  Dave being a woodworker, the mirror box is all wood including the mirror mount.  The 6 pt cell design is by Albert Highne, with the mirror being glued to the cell.  The lightweight upper end baffle is made from 1/16 inch thick wood.  This is Dave's third scope and weighs 78 pounds.

The walkabout ended with Ross Robert's 3-mirror 16 inch f/5.7 folded Dobsonian.   Ross, one of the excellent Portland, Oregon, telescope makers, designed this scope to be optically folded, resulting in a reduced height of 3 feet.  Like others, first light was last night!  Ross uses a SiderealTechnology drive, with full goto and tracking.  Ross designed a 27 pt cell for the 1.6 inch thick Swayze refigured mirror.  The secondary is 5.7 inch size, made by Discovery Optics, and relatively expensive.  At full vertical height, Ross sits down to look through the eyepiece.  In fact, the eyepiece has very little movement to it as the scope is moved from horizontal to vertical.  Like Dethloff and others, Ross uses a full eyeshroud to improve viewing of extremely dim objects.  Ross reports that optical alignment can be tricky.

This concludes the walkabout.  Here's another interesting scope from the 2008 the Oregon Star Party.  This is a 16 inch that features a single arm fork mount, designed and manufactured by Greg Babcock back in the 1970's.  The mounting was pulled from long term storage at the local planetarium by Tom Conlin.  Tom's mirror cell is beautifully machined.  It too is a string scope.

Sky and Telescope's report of the 08 OSP http://www.skyandtelescope.com/news/27768494.html
Pics AND video of the walkabout http://thebrownings.name/med/