Orion STARBLAST 9814 - Manual (Page 11)

11
Aligning the Primary Mirror
The final adjustment is made to the primary mirror. It will need
adjustment if, as in Figure 10d, the secondary mirror is cen-
tered under the focuser and the reflection of the primary
mirror is centered in the secondary mirror, but the small reflec-
tion of the secondary mirror (with the “dot” of the collimation
cap) is off-center.
The tilt of the primary mirror is adjusted with three spring-
loaded collimation thumbscrews on the back end of the optical
tube (bottom of the primary mirror cell); these are the wide
thumbscrews. The other three thin thumbscrews lock the mir-
ror’s position in place; these thin thumbscrews must be
loosened before any collimation adjustments can be made to
the primary mirror.
To start, turn the thin thumbscrews that lock the primary mir-
ror in place a few turns each. (Figure 13)
Now, try tightening or loosening one of the wide collimation
thumbscrews with your fingers (Figure 14). Look into the
focuser and see if the secondary mirror reflection has moved
closer to the center of the primary. You can tell this easily with
the collimation cap and mirror center mark by simply watching
to see if the “dot” of the collimation cap is moving closer or fur-
ther away from being centered in the “ring” of the primary
mirror mark. When you have that dot centered as much as is
possible in the ring, your primary mirror is collimated. The view
through the collimation cap should resemble Figure 10e. Re-
tighten the locking thumbscrews.
A simple star test will tell you whether the optics are accurate-
ly collimated.
Star-Testing the Telescope
When it is dark, point the telescope at a bright star and accurate-
ly center it in the eyepiece’s field of view. Slowly de-focus the
image with the focusing knob. If the telescope is correctly colli-
mated, the expanding disk should be a perfect circle (Figure 15).
If the image is unsymmetrical, the scope is out of collimation. The
dark shadow cast by the secondary mirror should appear in the
very center of the out-of-focus circle, like the hole in a donut. If
the “hole” appears off-center, the telescope is out of collimation.
If you try the star test and the bright star you have selected is not
accurately centered in the eyepiece, the optics will always
appear out of collimation, even though they may be perfectly
aligned. It is critical to keep the star centered, so over time you
will need to make slight corrections to the telescope’s position in
order to account for the sky’s apparent motion.
Appendix B: Cleaning the
Optics
Cleaning Lenses
Any quality optical lens cleaning tissue and optical lens clean-
ing fluid specifically designed for multi-coated optics can be
used to clean the exposed lenses of your eyepieces. Never
use regular glass cleaner or cleaning fluid designed for eye-
glasses
Before cleaning with fluid and tissue, blow any loose particles
off the lens with a blower bulb or compressed air. Then apply
some cleaning fluid to a tissue, never directly on the optics.
Wipe the lens gently in a circular motion, then remove any
excess fluid with a fresh lens tissue. Oily fingerprints and
smudges may be removed using this method. Use caution;
rubbing too hard may scratch the lens. Never reuse tissues.
Cleaning Mirrors
You should not have to clean the telescope’s mirror very often;
normally once every year or so. Covering the telescope with
the dust cap when it is not in use will help prevent dust from
accumulating on the mirrors. Improper cleaning can scratch
mirror coatings, so the fewer times you have to clean the mir-
rors, the better. Small specks of dust or flecks of paint have
virtually no effect on the visual performance of the telescope
The large primary mirror and the elliptical secondary mirror of
your telescope are front-surface aluminized and over coated
with hard silicon dioxide, which prevents the aluminum from
Figure 13.
The three thin
thumbscrews that
lock the primary
mirror in place
must first be
loosened before
any adjustments
can be made.
Figure 14.
The tilt of the
primary mirror is
adjusted by
turning one or
more of the three
wide collimation
thumbscrews.
Figure 15. A
star test will
determine if the
telescope's optics
are properly
collimated. An
unfocused view of a
bright star through the eyepiece should appear as illustrated on the
right if optics are perfectly collimated. If the circle is unsymmetrical,
as illustrated on the left, the scope needs collimation.
Out of collimation Collimated