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16" Truss Dob

 

16-2-25-08 3D

During the winter of 2008, while looking for a small diameter glass blank to make my own mirror, I lucked into a Meade DS-16 mirror set, a 16” primary and a 4” secondary pair.  The first owner of had used the DS-16 for years.  It was permanently mounted outside, in his back yard, and was stored under a tarp.  It was just too heavy to bring inside.  After years of enjoyment, the Sonotube construction fell prey to the humid conditions under the tarp near the Barnegat Bay.  The original owner salvaged the 16” primary, the 4” secondary and the 1 ¼” rack & pinion focuser.  He carefully boxed them up and stored them in his garage under his work bench.  Many years later, he saw my post asking if anyone had a glass blank, and luckily for me, thought maybe I would like those old parts he had stored in his garage for years. 

 Believe or not, I was reluctant to begin such an ambitious first telescope project.  He showed me his own 13” home made truss dob.  He even let me take pictures of it so I could copy it for a 16” version.  I decided to buy the mirror pair and give building one a try.  When would I get another chance to own a large aperture telescope for a price of a small one?  Besides, my generation grew up believing you can build anything out of plywood.

 Mirror Box Bare Bones
 Top Cage Bare Bones

 The mirror box was glued and finish nailed together.  It was  squared and held in place while the glue dried.  An internal support rail of fir was installed to stiffen box and to support mirror cell later.

 The top cage was made of 1/4" plywood.  The top rings were cut using a router on a radius arm allowing finished rings in near perfect circular shape.  These were glued and finish nailed together with short 3/4" square connector blocks at the end of each columns. Tee Bar 
 Cell A six point mirror cell mounted on aluminum tee support beams.  The cell rocker supports were made using 1/2" plywood.  Three 1/4" thick plywood links were installed to hold the rocker supports in their respective and proper positions.  This cell has top side collimation inside the mirror box allowing adjustments to the primary mirror alignment without having to get down under the mirror box to do so.  This arrangement also saved a few inches overall height too.
 Cell in Mirror Box Bottom  Cell in Mirror Box Front
Mirro in Box Front  A mirror support strap was made using perforated pipe hanger stock purchased at the local hardware store.  Two turnbuckles were added at each end of the support strap for mirror centering adjustment. 
 Trial Fit 1
 The altitude bearing were cut from 3/4" plywood.  Later lifting handles are cut into each.  The photos above show their positions during the initial trial fit.  The final assembly was made using (3) 1/4" bolts.
The hardest parts to make were the truss pole clamps. Bottom clamps left, top right. Made using a 2x4.  Holes were drilled using a spade bit in a drill press.  The blocks were then ripped two halves on a table saw  Rough Cut Clamps
 Bottom Clamps Installed  Top Clamp on Top Cage
Truss pole clamps installed inside mirror box.  Placing them inside the mirror box greatly simplified the connection of the altitude bearing on the outside of the mirror box. Truss pole clamps were also installed at the bottom of each top cage columns.
Spider and Cage  Top Collimation 
Spider and secondary holder are shown above.  The secondary mirror support was made from a short section of 4" diameter PVC pipe.  The spider was made using perforated bar stock and was anchored to the top cage columns using bolted "L" brackets.  Two 3/4" thick plywood discs form the main hub at the center of the spider.  The center 1/4" bolt clamps the assembly together.  Three other 1/4" bolts provide collimation alignment of the secondary.  No tools are needed in the field to collimation the telescope. 
Side Bumper  Top Bumper 
Side and top bumpers were made and installed to help steady the mirror during transport.  During final assemble gaps were left between these bumpers and the outside of the mirror to allow free movement of the primary during collimation. 
First Light 1

 First light of the not yet completed telescope was August, 2008.

 

What a relief when it focused on that first bright star to a near pin-point.  

 

I actually made a telescope.....

A 1/4" plywood deck with removable cover was added.  This deck protects the primary mirror during setup, breakdown, transport and storage.  Mirror Cover 
All wood parts were coated with two coats of clear polyurethane to improve their resistance to those damp nights.  Poly 
Cloudy Night Waiting RACI 1
The top cage nests nicely on top of the mirror box for storage.  To finish up the top cage a plastic shroud was added to block stray light from the view of the eyepiece. This shroud was painted black inside using Fusion type paint.  Both Telrad and 9x50 RACI finders were added for star hopping.  Later Digital Setting Circles were added.
Waiting for Dark

Many years later this 16" telescope continues to pay off for me.  It is still my favorite telescope and a big hit at any star party I attend.

I had plenty of good advice and even a few hours of hands on help from my good friends at STAR and ASTRA Astronomy Clubs in New Jersey.