Appendix A: Collimation (Aligning The Mirrors) - ORION TELESCOPES & BINOCULARS SpaceProbe 3 Altaz 9845 Instruction Manual

Appendix A:
Collimation -
Aligning the
Mirrors
Collimation is the process of
adjusting the mirrors so they are
perfectly aligned with one anoth-
er. Your telescope's optics were
aligned at the factory, and should
not need much adjustment
unless the telescope is handled
roughly. Accurate mirror align-
ment is important to ensure the
peak performance of your tele-
scope, so it should be checked
regularly. Collimation 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 primary mirror
centered in the secondary mirror,
and the reflection of the second-
ary mirror (and your
centered in the reflection of the
primary mirror, as in Figure 6a. If
anything is off-center, proceed
with the following collimation pro-
cedure.
The Collimation Cap and
Mirror Center Mark
Your SpaceProbe 3 comes with a
collimation cap. This is a simple
cap that fits on the focuser draw-
tube like a dust cap, but has a
hole in the center and a silver
bottom. This helps center your
eye so that collimation is easy to
perform. Figures 6b through 6e
assume you have the collimation
cap in place.
In addition to providing the colli-
mation 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 collimation 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 collimation cap is centered inside the ring. This
center mark is also required for best results with other colli-
a.
b.
eye)
d.
Figure 6. 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).
c.
e.
centered in the focuser drawtube, rotate the secondary mirror
holder until the reflection of the primary mirror is as centered
in the secondary mirror as possible. It may not be perfectly
centered, but that is OK. Now tighten the three small align-
ment screws equally to secure the secondary mirror in that
mating devices, such as Orion's
LaserMate 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 sec-
ondary 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 reflections 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 6b, it must be
adjusted. 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 tele-
scope tube opposite the focuser
(i.e., on the other side of the sec-
ondary mirror) will also be helpful
in collimating the secondary mir-
ror. Use a small Phillips head
screwdriver to loosen the three
small alignment screws in the
center hub of the 3-vaned spider
several turns. Now hold the mirror
holder stationary (be careful not
to touch the surface of the mir-
rors), while turning the center
screw with a larger Phillips head
screwdriver (see Figure
Turning the screw clockwise will
move the secondary
toward the front opening of the
optical tube, while turning the
screw counter-clockwise
move the secondary
toward the primary mirror.
When the secondary mirror is
7).
mirror
will
mirror
9