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This section is on the assembly of the Dobsonian upper box that rides on the Azimuth base and support the Elevation
rotators and telescope tube assembly.
The Dobsonain (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 circle.
The Dob upper box support is made
from 3 main pieces of plywood. The Dob box support has to tall enough so the
telescope tube can swing around the elevation (EL) rotation plastic pipe pieces. The
telescope tube will balance about in the middle of the tube. This depends on the weight of the mirror and mirror cell parts
at one end of the tube and the weight of the eyepiece holder and the secondary mirror and support.
Cut some plywood sides to
make a box tall enough for the telescope tube length to rotate in EL inside the 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 PVC 5”
pipe ends will ride in cut-outs on each side of the Dob box sides.
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 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 pipe fitting 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” or 8” on the
sides of the Dob box. When you paint the Dob tube be sure to pain on one end of the tube the telescope size 6” or 8”
and the F-number, F5 or F8.
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 this 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 6” or 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 Dobsonain around.
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| Figure 7: Attach the Dob carry handles as required |
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 warpping 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 mirrror cell, then the it will be ready to put in the telescope tube.
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