Orion 9966 Instruction Manual page 5

Figure 6. Lower the assembled mirror cell onto the tube
so one side of the end ring is seated on the tube edge. The
threaded attachment holes in the end ring should also be
lined up with the through holes in the end of the tube
of engagement on the shafts. The mirror cell is now ready to
be installed into the tube.
Assembling the SkyQuest XT12 mirror cell to the tube can be
a bit tricky. This is because the large diameter and thin steel
of the tube will cause the tube to become somewhat out of
round once the rear end ring is removed.
To assemble the mirror cell to the tube, stand the tube up
vertically so that the raw edge of the tube is facing upwards.
Line up the threaded holes in the edge of the mirror cell end
ring with the holes in the end of the tube. Then, lower the
mirror cell onto the tube so that one side of the end ring is
fully seated onto the tube (Figure 6). Now, look along the
perimeter of the tube, and you will notice a bulge in the tube
that prevents the mirror cell from fully seating on the tube
(Figure 7). Position your body so that your chest is pressing
against this bulge, and hug the telescope with your left hand
so that the tube becomes round. With your right hand, gently
tap down the side of the mirror cell that needs to be seated,
and the entire mirror cell should seat onto the tube (Figure 8).
Figure 8.
Hug the tube so that your chest pushes against the
bulge, and a gentle tap should fully seat the mirror cell onto the
tube.
Figure 7.
Locate the area of tube that is bulging out and
preventing the mirror cell from fully seating.
Replace the six Phillips-head screws that connect the rear
end ring to the tube.
Assembly of the Dobsonian base
Refer to Figure 9 during base assembly. The base need
only be assembled once, unless you disassemble it for long-
term storage. The assembly process takes about 30 minutes
and requires a Phillips screwdriver, an adjustable crescent
wrench, and the provided hex keys. When tightening screws,
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Figure 9.
Exploded view of the Dobsonian base.
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