Oregon Star Party Telescope Walkabout, 2017 edition

Running for more than 20 years, the Oregon Star Party Telescope Walkabout celebrates and promotes telescope making. As a group we walk from telescope to telescope, meeting each builder, listening to their story. What is it about? What works? What doesn't? What would they change next time? Sometimes it is a novel idea, sometimes it is a beginner's first effort. We ask questions as a group, benefiting collectively. The popularity of the walkabout over the years shows its value to amateurs. Ask yourself if you'd rather be answering judges questions or talking about your telescope to an appreciative crowd.

The Oregon Star Party has seen the invention and early adoption of flex rockers, string telescopes, Tensegrity tube structures, wire spiders, computerized drive systems, direct drive motors, TrackBalls, SudiBalls, ultra-lights, three large one meter reflectors, super fast sub-F3 reflectors, folding light path reflectors, travel and folding scopes, novel observing accessories, meniscus mirrors, ultra-thin mirrors, Lurie-Houghtons and Schiefspieglers, a number of binoscopes, club scopes and tracking platforms. Especially we take time to celebrate 'first' telescopes made by kids and adults. Invariably there is a fresh take, a new approach or a novel idea.

This year the largest crowd we can recall participated. The Walkabout is the largest event outside of the star party's concluding door-prize event. We saw a number of cutting-edge telescopes as well as time tested traditionally designed telescopes. Note the increasing use of 3D printed parts. The builders and their telescopes featured this year are:

• Bruce Sayre's 14.25 inch F5 binocular telescope
• Greg Lobdell's on-site-repaired telescope
• Rob and Quinn Brown's Tensegrity 8 and 12 inch telescopes
• Kreig McBride's 8 inch refractor
• Dan Gray's alt-alt or el-el advanced computerized mounting
• Greg Rhode's ultra-lightweight aluminum 15 inch telescope
• Nels Johansen's 16 inch string telescope
• Mike Dilley's 12.5 inch F2.5 superfast, single arm equatorial telescope
• Sameer Ruiwale's 16 inch F4 Tensegrity telescope
• Andrew Cooper's hodge-podge tracker
• Michael McKeowns's 16 inch split-ring equatorial telescope

Mel Bartels and the gathering fellow walkabouters

Bruce Sayre's 14.25 inch F5 binocular telescope

• InterPupillary Distance (IPD) adjustment is a single knob
• Binocular alignment perfect (sub arc-second) through about 70% up and down vertical altitude
• Controls the scope through an iPhone running Sky Safari Pro (SSP)
• Vibration is controlled
• CAD designed
• Main assembly is 8022 extruded aluminum
• Uses 3D printed parts
• Blue steel spiders
• Scope disassembles for transport
• Half an hour setup using only thumb screws
• Base weighs 50 pounds
• 2.5x the cost of a single mirror'd scope
• Mirrors within 1/4 inch focal length of each other
• Exhibits stereopsis effects

Greg Lobdell's on-site-repaired telescope

• Accidently dropped an 8 inch Discovery scope and had to repair onsite during the star party
• Used sheet plywood and glue from nearby Home Depot
• Ebony Star formica already on hand
• The 2nd scope sports a 10 inch Coulter mirror

Rob and Quinn Brown's Tensegrity 8 and 12 inch F5 telescopes

• Considers Tensegrity string scope design mature after Don Peckham's pioneering design
• Tensegrity means 'tension integrity' and uses struts in compression and guy wires in tension
• The 12 inch uses a doubled skirt while the 8 inch uses a single skirt
• Both scopes use a wire spider
• The 12 inch uses wire in tension wrapped around the upper end
• The unique periscope-finder located at the bottom of the tube assembly looks up through the Telrad
• Uses 3D printed parts
• One eyepiece is 3D printed
• The 12 inch weighs about 50 pounds
• Quinn's first scope is the 8 inch
• Quinn recommends starting maybe not quite so advanced
• Both mirrors are homemade

Kreig McBride's 8 inch refractor

• 8 inch refractor is three deaces old
• Purchased the Optical Tube Assembly (OTA) then modified and refurbished the aluminum tube assembly
• The mounting is based on Richard Berry's design
• Teflon and wood bearings
• Multi-eyepiece turret though doesn't fill it with expensive heavy eyepieces
• Enjoys planetary observing
• There's a little achromatic aberration but it is easily ignored

Dan Gray's alt-alt or el-el advanced computerized mounting

• Designed primarily for satellite tracking which when aligned azimuthly, can track in a single axis
• The advanced computer control doesn't need to be azimuthly aligned though to track satellites
• Has 'Dobson's Hole at the ends of the primary axis that point to the horizon
• Extremely fast and smooth direct drive brushless motors
• Homemade direct drive motors use magnets and coils along with an encoder
• Has motorized and computer controlled image rotator and focuser
• Can track consistently for five minutes with two arc second accuracy
• The control box sports a brushless controller than Dan designed
• The thrust and ball bearings sit independent of the mount/base and can be lifted away
• The axes names are 'primary' which points to the north/south horizon and 'secondary' which points at 90 degrees to the primary axis

Greg Rhode's ultra-lightweight aluminum 15 inch telescope

• Uses a Mark Cowan quartz mirror
• Designed and built to be the lightest and most rugged largest possible airplance transportable telescope
• Uses a wire spider as designed by Mark Cowan
• Square aluminum tube upper end
• Standard string scope design
• Upper end disconnects from the compression tubes and strings, then bolts to teh mirror box for checked airplane luggage
• Base is a minimalist flex rocker design
• Water hydration packs for counterweighting: emptied for transport, filled for use
• Uses 24 inch mountain bike rims and a 29 inch rim for the base
• Scope fits into 22 inch base drum carry case
• Greg lifts overhead to show how lightweight the 15 inch scope is - awesome

Nels Johansen's 16 inch string telescope

• Scope belongs to the Battle Point Astronomical Society near Seattle Washington
• Built to be a public loaner scope: very rugged and meant to be heavily used by club members
• 100 pound overall weight
• Unique offset altitude bearings: the arc is a modified sine curve with 7 inch offset
• The telescope cannot be tilted backwards off the rocker
• Compression tubes use threaded through bolts
• Bow string
• Heavy dew problem in local environment to heaters are everywhere on the scope including the eyepiece box
• Wires conduct electricity to the upper end
• Top cover includes a sun filter and a lunar sub-aperture opening
• Bearings are skateboard bearings on aluminum
• Five minute setup for one person

Mike Dilley's 12.5 inch F2.5 superfast, single arm equatorial telescope

• 32 inch focal length
• 2.5 degree Field of View (FOV)!
• Mirror needs another figuring session or two
• Will be equipped with an optional Cassegrain focus - not yet finished
• Byers drive
• Mount from composite wood and fiberglass
• The single arm fork is strong and balances well
• Can be setup in one minute

Sameer Ruiwale's 16 inch F4 Tensegrity telescope

• Saw first light at star party
• Had to shorten the strings just a bit
• Quartz mirror by Mark Cowan
• Reiner Vogel inspired mirror box with ideas from Judy Dethloff
• Primary mirror cell uses two front collimation screws, the 3rd point being a pivot
• Wire spider
• Custom 2-axis diagonal holder with simplified adjustment
• Bow string 'UltraCam' (no longer manufactured)
• SiTech drive system with clutches
• Very nice and compact motor and drive box design
• Long altitude drive shaft that extends across the rocker
• Weighs 50 pounds; about 10 pounds in the bottom base
• The tube assembly's compression tubes are not parallel, instead they lean inward a bit at the upper end so that the upper end can fit within the mirror box

Andrew Cooper's hodge-podge tracker

• Built to hold multiple lenses and scopes
• Tracking for deep corona exposures
• C8 mount with Meade wedge
• Parts from various scopes that saw unexpected ends (one caught on fire)
• Uses 'old-fashioned' 120 VAC synchronous motor
• Built his own custom controller than runs on 12V DC batteries
• Made new legs from solid wood for tripod support
• Uses some machined parts
• Custom Sun finder

Michael McKeowns's 16 inch split-ring equatorial telescope

• Spent a year designing and five years building
• Built for public events: had to look big and impressive
• Typically used at wineries so built so that drunks can lean on it without trouble
• Uses 18V DeWalt batteries from dead drills
• Uses a NetBook for wireless 'goto'
• Tube from redwood fence boards
• Tube was assembled, then spun while being sanded then epoxied
• Painted white for public with black eye for the focuser (hence, the nickname, 'Cyclops')
• 3-vane curved spider
• Mirror taken from another scope
• 18 point mirror cell
• Rotating tube in cage
• RA drive rim on the split-ring is an aluminum ring with a wire insert to pull it tight
• Base triangle is from wood cut to size so that eventually aluminum box can replace it
• Counterweighting is melted lead in MDF that was bend while hot
• Built trailer for transport; ramped in and out with tackle
• Tube weighs 450 pounds

Mel Bartels