12
Any deviation from concentricity of any of these
telescope parts with the eye requires adjustments
to the secondary mirror-holder (Fig. 23) and/or the
primary mirror cell (Fig. 24), as described below.
2. Secondary mirror-vane adjustments: If the
secondary mirror (1, Fig. 26) is above or below
center within the draw tube, thread inward one of
the spider vane adjustment/lock knobs (44, Fig.
5) while unthreading the opposite knobs. Only
make adjustments to two knobs at a time until the
secondary mirror appears as in Fig. 27.
3. Secondary mirror-holder adjustments:
If the secondary mirror (1, Fig. 27) is left or right
of center within the draw tube, adjust the center
phillips head screw on the secondary mirror holder
to move the secondary mirror into position. Do not
unthread the center mounting screw too much
or the secondary mirror holder can fall off of the
spider vanes completely.
If the secondary mirror (1, Fig. 27) is centered in
the focuser draw tube (2, Fig. 27), but the primary
mirror is only partially visible in the reflection (3,
Fig. 27), the three “+” (Phillips head) secondary
mirror-tilt screws (2, Fig. 23) should be slightly
unthreaded to the point where the secondary
mirror-holder (3, Fig. 23) can rotate about its axis
parallel to the main tube. Grasp the secondary
mirror-holder (avoid touching the mirror surface!)
with your hand and rotate it until, looking through
the draw tube, you can see the primary mirror
centered as well as possible in the reflection of the
secondary mirror. With the rotation of the secondary
mirror-holder at this best-possible position, thread
in the three Phillips head screws (2, Fig. 23) to lock
the rotational position. Then, if necessary, make
adjustments to these three Phillips head screws to
refine the tilt-angle of the secondary mirror, until
the entire primary mirror can be seen centered
within the secondary mirror’s reflection. With the
secondary mirror thus aligned the image through
the draw tube appears as in Fig. 28.
4. Primary mirror adjustments: If the secondary
mirror (1, Fig. 28) and the reflection of the primary
mirror (2, Fig. 28) appear centered within the
draw tube (3, Fig. 28), but the reflection of your
eye and the reflection of the secondary mirror (4,
Fig. 28) appear off-center, then the primary mirror
tilt requires adjusting. Use the primary mirror
collimation adjustment knobs to tilt the mirror.
Note: Always loosen the collimation lock knobs
before adjusting the primary mirror tilt.
The primary mirror-tilt screws are located behind
the primary mirror, at the lower end of the main
tube. See Fig. 29.
Before adjusting the primary mirror-tilt screws, first
unscrew by several turns the three primary mirror
lock screws (Fig. 29) which are also located on the
rear surface of the primary mirror cell and which
alternate around the cell’s circumference with the
three adjustment knobs. Then by trial and error turn
the primary mirror adjustment knobs (Fig. 29) until
you develop a feel for which way to turn each knob
to center the reflection of your eye in the draw tube.
(An assistant is helpful in this operation.) With your
eye centered as shown in Fig. 25, turn the three
primary mirror lock knobs (Fig. 29) to re-lock the
tilt-angle of the primary mirror. The telescope’s
optical system is now aligned. This collimation
should be checked after each optical tube setup
and from time to time, with small adjustments (per
steps 1, 2, 3, and/or 4, above) effected as required
to keep the optics well-aligned.
Figure 29
Collimation lock
knobs
(without springs)
Collimation
adjustment
knobs
(with springs)
ENHANCED COLLIMATION
An enhanced collimation of the optics can be
performed by having the secondary mirror holder
offset from its concentric position with respect to
the focuser draw tube. The Meade LightBridge
Plus is slightly different from that of other Newtonian
