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The Dobsonian plywood box parts list:
1. One sheet of 2 foot x 4 foot by 3/4" thick plywood. Get the best water
proof grade of plywood you can.
2. Dry wall screws to attach the plywood together and to the 18" wood circle.
3. Obtain a good wood glue for gluing the wood edges together.
4. PVC Elevation pipe rotator cups. These are found in the plumbing
department as 4" or 5" plastic pipe caps. The size you need depends on the weight of the telescope.
5. Varnish and paint to paint the wood.
6. A jig saw cutter, drill, drills for pilot holes of the dry wall screws,
and miscellaneous stuff.
This section is on the assembly of the Dobsonian upper
Elevation box that rides on top of the Azimuth base and supports the Elevation pvc rotator cups attached
to the telescope tube assembly.
The Dobsonian (Dob)
telescope will sit atop a plywood box support. The wood box sides are screwed
together at the edges and then screwed to the 18” wood azimuth rotator circle.
The
Dob upper box support is made from 3 pieces of plywood. The Dob box support has
to be tall enough so the telescope tube ( 30" long ) can swing in the elevation (EL) direction with out hitting the 18" circle
or the bolt sticking up.
The telescope tube will balance about in the middle of its tube. The balance depends on the weight
of the mirror and its mirror cell parts at the bottom end of the tube, and the weight of the eyepiece
focuser holder and the secondary mirror spider support at the top end of the tube. You will balance the tube later on the
final assembly page.
Cut
some plywood sides to make a box tall enough for the telescope tube length so it can rotate in the elevation
direction inside the Dob box.
A single sheet of
2 foot by 4 foot by ¾” plywood can be cut to make a Dob box about 2 feet tall. This will support a balanced telescope
tube about 40” long.
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| Figure 1: 2x4 sheet of 3/4" plywood cut for Dob upper box |
The Dob telescope
tube will have 5" pvc cup ends bolted on each side. The pvc cups will ride in cut-outs on each side of the Dob box panels.
Before you assemble
the Dob box sides you need to cut the semi circles where the Dob tube PVC plastic cups will sit. Mark the semicircles into the top center of each side of the Dob box.
Cut the arcs out with a jig saw.
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| Figure 2: Cut the Elevation rotator circles in the Dob support box |
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| Figure 3: Dob Elevation rotator PVC cap fittings that bolt to the telescope tube sides |
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| Figure 4: Dob elevation rotators held in place by pipe tape |
Once all the plywood
is cut, be sure to varnish the plywood on all sides. Then you can paint the plywood
any Astronomical colors you like.
Please paint the
names of the 101 Class participants, the AVC College Logo, the Year and Date, and the Dobsonian telescope size 6” on
the sides of the Dob box.
When you paint the
Dob tube be sure to paint on one end of the tube the telescope size 6” and the F-number F5.
Using the marked
Dob box plywood lines you made on the 18” wood azimuth circle drill holes about every 3” along the edges of the
plywood to allow the dry-wall screws to pass through to the Dob box plywood without cracking the wood. Drill holes that are just smaller than the dry wall screws diameter.
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| Figure 5: Dob AZ base where the Dob EL support box attaches |
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| Figure 6: The unpainted Dob support box plywood assembled on the AZ rotator wood circle |
The unpainted Dob
box should look about like Figure 6 when it is assembled on the 18” wood rotation circle.
A modification was
necessary to the Dob box front and the Dob box back. If you look at figure 6 you see that the Dob box back plywood is flat
at the top. If you want to rotate the telescope in elevation to near horizontal
you will see that it hits the top of the Dob back box plywood.
Use the 8”
Dob tube and mark a semi-circle on the Dob box back plywood. Then using a jig saw cut out the arc. This will allow the telescope
to view near the horizon.
Another addition
to the Dob box are handles on each side of the Dob box sides. Mount the handles so you can carry the Dobsonian around.
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| Figure 7: Attach the Dob carry handles as required |
You can add some extra wood support to the front of the Dob
box. Once the telescope tube is balanced and assembled you can add a piece of plywood across the bottom front of
the Dob box. This will help strengthen the box.
To keep the telescope tube from falling out of the Dob
box you can add some plywood with cut outs that go over the pvc rotator cups. See figure 8. You can hinge one end of
the plywood and put a clasp on the other end.
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| Figure 8: Dob box EL rotator clamp plywood boards |
You are now done with the Dobsonian upper box support parts.
Be sure to paint all the wood parts so that water will not penetrate the wood and cause problems and warping of the wood.
Paint the Dob base circles and the upper box support, then
add the class names of the fabricators, the college logo, the date and semester of the assembly.
The next item for assembly is the telescope mirror cell, then
it will be ready to mount inside the telescope tube.
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