Orion SKYQUEST XT8 - Manual (Page 13)

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the collimation cap and Mirror center Mark
Your SkyQuest telescope comes with a quick collimation cap.
This is a simple cap that fits on the focuser drawtube like a
dust cap, but has a hole in the center and a reflective inner
surface. The cap helps center your eye so that collimation is
easier to perform. Figures 18b through 18e assume you have
the collimation cap in place.
As an additional aid in collimation, the primary mirror of every
SkyQuest telescope has a tiny adhesive ring marking its
exact center. This center ring will not affect the images you
see when observing with the telescope in any way (since it
lies directly in the shadow of the secondary mirror), but will
greatly facilitate collimation when using the supplied collima-
tion cap or other, more sophisticated collimation devices such
as the Orion LaserMate Laser Collimator. The center ring
need not be removed from the primary mirror!
Preparing the telescope for collimation
Once you get the hang of collimation, you will be able to do it
quickly even in the dark.
For now, it is best to collimate in daylight, preferably in a bright-
ly lit room and with the telescope 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 fall-
ing down onto the primary mirror and causing damage, should
something come loose when 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 col-
limation, your telescope should resemble Figure 19.
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, in the direction parallel to the
length of the telescope. If it isn’t, as in Figure 18b, it must be
adjusted. This adjustment will rarely, if ever need to be done.
Using a 2mm hex key, loosen the three small alignment
set screws in the center hub of the 4-vaned spider several
turns. Now keep the mirror’s holder stationary (be careful not
to touch the surface of the mirrors), while turning the cen-
ter screw with a Phillips head screwdriver (See Figure 20).
Turning the screw clockwise will move the secondary mirror
toward the front opening of the optical tube, while turning
the screw counter-clockwise will move the secondary mirror
toward the primary mirror.
Note: When making these adjustments, be careful not to
stress the spider vanes or they may bend.
Figure 19. The SkyQuest
IntelliScope 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.
Figure 20. To center the secondary mirror under the focuser, hold
the mirror holder in place with one hand while adjusting the center
bolt with a Phillips screwdriver. Do not touch the mirror’s surface!
Figure 21. Adjust the tilt of the secondary mirror by loosening or
tightening the three alignment set screws with a 2mm hex key.