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well-resolved image will show more detail and provide a more
enjoyable view than a dim and fuzzy, overmagnified image.
collimating the optics
(aligning the Mirrors)
Collimating is the process of adjusting the mirrors so they
are aligned with one another. Your telescope's optics were
aligned at the factory, and should not need much adjustment
unless the telescope is handled roughly. Accurate mirror
alignment is important to ensure the peak performance of
your telescope, so it should be checked regularly. Collimating
is relatively easy to do and can be done in daylight.
To check collimation, remove the eyepiece and look down
the focuser drawtube. You should see the secondary mirror
centered in the drawtube, as well as the reflection of the pri-
mary mirror centered in the secondary mirror, and the reflec-
tion of the secondary mirror (and your eye) centered in the
reflection of the primary mirror, as in Figure 3a. If anything is
off-center, proceed with the following collimating procedure.
the collimation cap and Mirror center Mark
Your 130mm reflector 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 silver bottom. This
helps center your eye so that collimating is easy to perform.
a.
Figure 3.
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).
6
Figures 3b through 3e assume you have the collimation cap
in place.
In addition to providing the collimation cap, you'll notice a tiny
ring (sticker) in the exact center of the primary mirror. This
"center mark" allows you to achieve a very precise collima-
tion of the primary mirror; you don't have to guess where the
center of the mirror is. You simply adjust the mirror position
(described below) until the reflection of the hole in the col-
limation cap is centered inside the ring.
Note: The center ring sticker need not ever be removed from
the primary mirror. Because it lies directly in the shadow
of the secondary mirror, its presence in no way adversely
affects the optical performance of the telescope or the
image quality. That might seem counterintuitive, but it's true!
aligning the secondary Mirror
With the collimation cap in place, look through the hole in
the cap at the secondary (diagonal) mirror. Ignore the reflec-
tions for the time being. The secondary mirror itself should
be centered in the focuser drawtube, in the direction parallel
to the length of the telescope. If it isn't, as in Figure 3b, it
must be adjusted. Typically, this adjustment will rarely, if ever,
need to be done. It helps to adjust the secondary mirror in a
brightly lit room with the telescope pointed toward a bright
surface, such as white paper or wall. Placing a piece of white
paper in the telescope tube opposite the focuser (i.e., on the
other side of the secondary mirror) will also be helpful in col-
limating the secondary mirror. Using a 2mm Allen wrench,
Reflective surface
of collimation
drawtube
cap
Reflection
of primary
mirror clip
b.
d.
Primary mirror
center mark
c.
e.
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