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Figure 32.
This image shows the XX12 properly set up for
collimation. Note the white paper placed across from the focuser
and the level angle of the optical tube. Ideally, the telescope should
be pointing at a white wall.
more sophisticated alignment devices, such as the Orion
LaserMate Laser Collimator.
Preparing the telescope for collimating
Once you get the hang of collimating, you will be able to do
it quickly even in the dark. For now, it is best to collimate in
daylight, preferably in a brightly lit room and aimed at a white
wall. It is recommended that the telescope tube be oriented
horizontally. This will prevent any parts from the secondary
mirror from falling down onto the primary mirror and caus-
ing damage if something comes loose while you are making
adjustments. Place a sheet of white paper inside the optical
tube directly opposite the focuser. This will provide a bright
"background" when viewing into the focuser. When properly
set up for collimation, your telescope should resemble Figure
32.
aligning the secondary Mirror
With the collimation cap in place, look through the hole in the
cap at the secondary (diagonal) mirror. Ignore the reflections
for the time being. The secondary mirror itself should be cen-
tered in the focuser drawtube. If it isn't, as in Figure 31b, its
position must be adjusted. This positional adjustment of the
secondary mirror will rarely, if ever, need to be done.
To adjust the secondary mirror left-to-right in the focuser draw-
tube, use the included 2mm hex key to loosen the three small
alignment set screws in the center hub of the 4-vaned spider
several turns. Now, grasp the mirror to prevent it from rotating
(be careful not to touch the surface of the mirror), while turn-
ing the center screw with a Phillips head screwdriver (Figure
33). Turning the screw clockwise will move the secondary mir-
ror toward the front opening of the optical tube, while turning
the screw counter-clockwise will move the secondary mirror
toward the primary mirror. When the secondary mirror is cen-
tered left-to-right in the focuser drawtube, rotate the second-
ary mirror holder until the reflection of the primary mirror is as
centered in the secondary mirror as possible. It may not be
perfectly centered, but that is OK for now. Tighten the three
Figure 33.
To center the secondary mirror under the focuser, hold
the mirror holder in place with one hand while adjusting the center
screw with a Phillips screwdriver. Do not touch the mirror's surface!
Spider vane
thumb nuts
Figure 34.
To center the secondary mirror up-and-down in the
focuser drawtube, make adjustments to the two knurled spider vane
thumb nuts that are perpendicular to the focuser.
small alignment set screws equally to secure the secondary
mirror in that position.
Note: When making these adjustments, be careful not to
stress the spider vanes or they may bend.
To adjust the secondary mirror up-and-down in the focuser
drawtube, adjust the length of the two spider vanes perpen-
dicular to the focuser. This is done by adjusting the knurled
thumb nuts that secure the vanes to the tube (Figure 34).
Loosen one thumb nut, then tighten the other until the sec-
ondary mirror is centered in the drawtube. Do not loosen the
thumb nuts too much, as they will completely unthread from
the ends of the spider vanes.
17
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