6 inch dob telescope
6
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The Builder
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Building a
Telescope:
Intro
Tube
Rocker Box
Base
Mirror Cell
Secondary Holder
Focuser
Finishing

Other projects:
Folding Table
Denver
Observing Chair

Aluminum
Observing Chair

Bino Chair
Portable
Observatory

Adirondack Chair
Josh's Stool

Resources:
My Buddy Shane
Chuck Fellows
Newt Software
Siebert Optics
Orion Telescopes

Building the Base

Coopered Tube Telescope
The basic wood material used for this telescope. Two 18" laminated ponderosa pine table tops, 1/4" x 6" x 48" poplar and oak, 3/4" x 12" x 24" oak plank all purchased at Lowe's. The table tops make the base and azimuth joint. The 1/4" poplar and oak are used for the tube slats. The oak plank is for the various parts of the base. Not shown is one 3/4" x 12" x 6' laminated knotty pine was used for the rocker box.
Coopered Tube Telescope

Coopered Tube Telescope

The base is made of clear 1" x 4" pine and from the oak planks. The radius of the top rockers are 3" to match the PVC mounted on the rocker box. The same radius is used on the top ends where the oak and pine is joined together. The oak inserts are joined both top and bottom with 3/8" dowels and glue. NOTE: If I ever join this way again I will purchase a bisket cutter. I didn't have a dowel jig and it was a pain resulting in a lot of sanding to get the joints perfectly smooth.
The cross pieces, made from 3/4" oak plywood, are joined to the uprights with brass screws and finish washers. A very elegant look when it was finished.
The uprights were joined to the top round base with countersunk screws from underneath. I chose not to glue these pieces to the base in case the base needed to be changed for some reason.
Coopered Tube Telescope
Felt was added to the rocker portions of the uprights for the PVC to glide on. I tried it without the felt and found it to not be completely smooth. The felt made it like oiled glass. The round felt pads are to provide protection when placeing the rocker box on the base and more importantly to provide a smooth bearing surface when moving the scope in elevation. I found that azimuth slewing could move the box all the way to one side or the other causing binding. The felt pads did away with that problem completely.
Coopered Tube Telescope

Coopered Tube Telescope
I used angled leg bases from Lowe's, placed at 120 degrees around the base, and oak legs with corresponding angles cut to make the legs.
I purchased the shortest legs I could find and then cut them to the shortest effective length to keep the scope as low as possible.
Be sure and screw the legs onto their bases and then mark them so the angle you grind, sand or cut is on the correct side of the legs. I marked each base with a number corresponding to its' leg so that when they are screwed in for the final time the angle is where it should be.
Coopered Tube Telescope

Coopered Tube Telescope

The table tops were stacked with center marked very accurately on the top circle. A pilot hole was drilled in the top one and then both were aligned, clamped together and drilled at the same time. I figured this was key to keeping the alignment between the two discs the same and making the azimuth slewing smoother.
A record was used for the bottom weight bearing surface and teflon furniture leg pads were screwed into the bottom of the top disc. DO NOT use the picture as a referrence. I figured that if 3 pads were enough 8 would be better. WRONG! Stick with three at 120 degree intervals. A little WD40 and this things slews like oiled glass.
The bottom of the bottom disc was countersunk for a 2 1/5" long 5/16" screw the same as used on the rocker box to hold the circles on. A brass flat washer and wing nut were used to attach the two tops together and set tension for rotation.
Coopered Tube Telescope
View of the base with the tube setting in place.
Coopered Tube Telescope Coopered Tube Telescope
I cut a block for mounting the brass plaque we had made. It adds a nice finishing touch to the scope and of course dates the scope which is really a piece of furniture that my daughter will keep for years.

Telescope Improvements
Dobsonian elevation altitude bearings

OK, the felt I installed for the elevation bearing surface was good at first. After a month or two of heavy use the felt took a set and began to jump or jolt into movement which was very annoying. I replaced the felt with long narrow furniture glides from Lowe's. They worked better but I could not get them mounted firm enough and the scope actually lost some stability. Buddy Shane had been to the local plastic supplier and picked up a piece of 1 1/4" teflon pipe. I cut a short piece of it, cut the piece into quarters, sanded the back to match the curve of the base, drilled and counter sunk a hole for mounting. I cannot describe how absolutely effortless the elevatin now works. PVC on teflon rules. So far I have not had a problem with balance EP to EP but the initial balance is critical enough that I marked the OTA placement in the rocker box with tape to make acheiving balance when installing the OTA easy.
Dobsonian telescope base azimuth bearings

Dobsonian telescope mount

Waterboard dobsonian azimuth bearing

Now that the elevation was amazingly smooth and reistance free, the azimuth, by comparison, was too stiff so of course I had to tinker with it. I tried a sheet of UHMW which decreased the friction as opposed to the record but was not satisfied with the smoothness and it seemed to have some backlash due to the surface. I thought sanding might help, it did not. The friction actually increased again so I decided to go back to a record. Having thrown the first record away a trip to the thrift store yielded one for $0.05 but alas the "stiction" was more than the first. A few months of use and it got worse due to wear and dust and grime. Cleaning did not help.

I replaced the record with waterboard and the small furniture glides with 2 1/8" diameter ones purchased at Lowe's and the azimuth is perfectly smooth with no "stiction" at all.

The sticky back foam on the furniture glides caused some stability issues but after sitting overnight the foam seems to have compressed some and stability gotten better. Will give it a few weeks with wieght on it to compress and I think it will be fine. It was taking over 3 seconds for vibration to settle out and now is down to two.

telescope eyepiece rack telescope eyepiece rack
After fumbling around in the dark for a year for eyepieces set on the base and grumbling everytime I knocked one off in the dirt I built an eyepiece rack.
I added a red LED light for thos really dark nights/places and yes, I'll stain and finish it at some point.