Orion 8 EQ - Manual (Page 12)

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 collimation
procedure.
Note About the Collimatable 2" Focuser
The SkyView Pro 8’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 collimation 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 SkyView Pro 8 EQ 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 collimation 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
counterintuitive, 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 key, 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 screwdriver
(See Figure 15). Turning the screw clockwise will move the
secondary mirror toward the front opening of the optical tube,
while turning the screw counter-clockwise will move the sec-
ondary mirror toward the primary mirror.
Note: When making these adjustments, be careful not to
stress the spider vanes or they may bend.
When the secondary mirror is centered in the focuser draw-
tube, 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 alignment screws equally to secure the
secondary mirror in that position.
If the entire primary mirror reflection is not visible in the sec-
ondary mirror, as in Figure 14c, you will need to adjust the tilt
of the secondary mirror. This is done by alternately loosening
one of the three alignment set screws while tightening the
other two, as depicted in Figure 16. The goal is to center the
primary mirror reflection in the secondary mirror, as in Figure
14d. Don’t worry that the reflection of the secondary mirror
(the smallest circle, with the collimation cap “dot” in the cen-
ter) is off-center. You will fix that in the next step.
12
Figure 15. To center the secondary mirror under the focuser,
hold the secondary mirror holder in place with one hand while
adjusting the center bolt with a Phillips screwdriver. Do not touch the
mirror’s surface!
Figure 16. Adjust the tilt of the secondary mirror by loosening or
tightening the three alignment set screws with a 2mm hex key.