Alignment (collimation) of the optical system – Orion XT10 User Manual
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4. Alignment (Collimation)
of the Optical System
To get the sharpest images, your telescope’s optical system
must be in precise alignment. The process of aligning the
primary and secondary mirrors with each other and with the
mechanical axis of the telescope is called collimation.
Your telescope’s optical system was collimated at the fac-
tory and will probably not need any further adjustment. But
rough handling during shipment can knock the optics out
of alignment, in which case you will need to recollimate the
system. Collimation is relatively easy to do and can be done
in daylight. It is a good idea to check the collimation of your
telescope before each observing session and make any nec-
essary adjustments.
To check collimation, remove the eyepiece and look down the
focuser drawtube. You should see the secondary mirror cen-
tered in the drawtube, as well as the reflection of the primary
mirror centered in the secondary mirror, and the reflection of
the secondary mirror (and your eye) centered in the reflection
of the primary mirror, as depicted in Figure 18a. If anything
is off-center, as in Figure 18b, proceed with the following col-
limation procedure.
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.
drawtube
Reflection
of primary
mirror clip
Figure 18. Collimating the optics.
(a)
When the mirrors are properly aligned, the view down the focuser drawtube should
look like this.
(b)
With the collimation cap in place, if the optics are out of alignment, the view might look something like this.
(c)
Here, the secondary mirror is centered under the focuser, but it needs to be adjusted (tilted) so that the entire primary
mirror is visible.
(d)
The secondary mirror is correctly aligned, but the primary mirror still needs adjustment. When the primary
mirror is correctly aligned, the “dot” will be centered, as in
(e)
.
a.
b.
c.
d.
e.
Note: 10" model has 4 mirror clips