Orion 9768 Instruction Manual page 5

Figure 6.
The tilt of the secondary mirror is adjusted by
alternately tightening and loosening the three alignment setscrews
in the mirror holder.
C. Aligning the Primary Mirror
The final adjustment is made to the tilt of the primary mirror. To
perform this adjustment properly, you will need to make a col-
limation target for the front opening of the telescope tube. This
can be done by placing the telescope's dust cover on a piece
of paper and tracing the dust cover's outline. Make the outline
a circle; do not trace the dust cover's removal tabs. Cut the
circle out, and precisely fold it in half. Then fold the half-circle
precisely in half again, to create precise quarter circles. Unfold
the circle, and mark the intersection of the folds with a black
pen; this is the precise center of the target. Center the target
on the front opening of the telescope, and tape it onto the tube
so it is secure (Figure 7).
Fold lines
Figure 7.
To collimate the primary mirror, make a collimation
target and center it on the front opening of the optical tube. Tape the
target onto the tube.
Now, look into the collimation cap, and note the center spot on
the collimation target within the reflection of the primary mir-
ror. If the target's center spot lies directly on the primary mirror
center mark, the primary mirror is already aligned. If not, as in
Figure 4d, the tilt of the primary mirror will need adjustment until
the target and the primary mirror centers coincide.
The tilt of the primary mirror is adjusted with three spring-
loaded collimation thumbscrews on the back end of the optical
tube (bottom of the primary mirror cell); these are the larger
thumbscrews. The other three smaller thumbscrews lock the
mirror's position in place; these thumbscrews must be loos-
ened before any collimation adjustments can be made to the
primary mirror.
To start, turn the smaller thumbscrews that lock the primary
mirror in place a few turns each (Figure 8). Use a screwdriver
in the slots, if necessary.
Figure 8.
The three small thumbscrews that lock the primary
mirror in place must first be loosened before any adjustments can be
made. A flat head screwdriver may be used to loosen these screws.
Now try tightening or loosening one of the larger collimation
thumbscrews with your fingers (Figure 9). Look into the col-
limation cap and see if the target's center has moved closer
to the primary mirror's center. Continue making adjustments
to the thumbscrews until the target's center spot lies directly
on the primary mirror center mark, as in Figure 4e. When this
is accomplished, your primary mirror is collimated. Re-tighten
the primary mirror locking thumbscrews, and remove the col-
limation target from the front of the tube.
A simple star test will tell you whether the optics are, in fact,
accurately aligned with each other and the focuser. This is
recommended, as some slight "tweaks" to the telescope's col-
limation may be needed for optimal performance.
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