Orion XT12 - Manual (Page 10)

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1.25" eyepiece adapter. The other eyepiece can be placed in
the eyepiece rack until it is needed.
The basic assembly of your SkyQuest IntelliScope Dobsonian
is now complete. It should appear as shown in Figure 1. The
dust cap on the front of the telescope tube should always
remain in place when the telescope is not in use. It is also
a good idea to store eyepieces in an eyepiece case and to
replace the cover caps on the focuser and finder scope when
the telescope is idle.
3. Aligning (Collimating)
the Optical System
To get the sharpest images, your telescope’s optical sys-
tem 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 collimating.
Collimating is relatively easy to do and can be done in day-
light or at night.
Because the primary mirror is shipped separately from the
optical tube, the telescope’s optics must be collimated before
it can be used. Most of the adjustments will be to the tilt of the
primary mirror, as the secondary mirror has been pre-aligned
at the factory. It is also good idea to check the collimation
(optical alignment) of your telescope before each observing
session and make any necessary 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 21a. If anything
is off-center, as in Figure 21b, proceed with the following col-
limation procedure.
The Collimation Cap and Mirror Center Mark
Your SkyQuest XT12 IntelliScope comes with a 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 collimating is
easier to perform. Figures 21b through 21e assume you have
the collimation cap in place.
As an additional aid in collimating, the primary mirror of the
SkyQuest XT12 IntelliScope 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 collimating when using the supplied collima-
tion cap or other, more sophisticated collimation devices such
as the Orion LaserMate Laser Collimator.
drawtube
Reflection
of primary
mirror clip
Figure 21. 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.