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7. Collimating
(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 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 in Figure 14a. If anything is off-cen-
ter, as in Figure 14b, proceed with the following collimating
procedure.
Note About the 2" Focuser
The Atlas 10 EQ’s 2" focuser can be collimated by 3 pairs of
push-pull screws located on the ring at the base of the
focuser (Figure 4). The focuser was collimated at the factory
and should never need to be adjusted. Focuser collimating is
only required under very rare circumstances but has been
made available for this telescope should such a need arise.
The Collimation Cap and Mirror Center Mark
Your Atlas 10 EQ comes with a collimation cap. This is a sim-
ple 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. Figures 14b
through 14e assume you have the collimation cap in place.
In addition to the collimation cap, the primary mirror is marked
with a circle at its exact center. This “center mark” allows you
to achieve a precise collimation of the primary mirror; you
don’t have to guess where the center of the mirror is. You sim-
ply adjust the mirror position (described below) until the
reflection of the hole in the collimation cap is centered in the
ring. The center mark is also required for best results when
using other collimating devices, such as Orion’s LaserMate
Laser Collimator, obviating the need to remove the primary
mirror and mark it yourself.
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 tele-
scope or the image quality. That might seem counter-
intuitive, but its 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 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 14b, it must be
adjusted. 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 towards a bright surface, such as
white paper or wall. Also placing a piece of white paper in the
telescope tube opposite the focuser (in other words, on the
other side of the secondary mirror) will also be helpful in colli-
mating the secondary mirror. Using a 2mm hex wrench,
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 center screw with a Phillips head
Figure 14.
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.
