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Figure 19. The optical tube's rear cell has three pairs of
collimation screws. The large knobs are the spring-loaded
collimation knobs while the smaller thumbscrews are the
locking screws.
the primary mirror to the center of the secondary mirror. But be
patient and you'll get it.
Aligning the Primary Mirror
The final adjustment is made to the primary mirror. It will need
adjustment if, as in Figure 17C, the reflection of the primary
mirror is centered in the secondary mirror, but the small reflec-
tion of the secondary mirror is off-center. The tilt of the primary
mirror is adjusted using three spring-loaded collimation knobs
and three smaller locking thumbscrews on the back end of the
optical tube (Figure 19). First loosen the three locking thumb-
screws a turn or so. Then tighten one of the collimation knobs
about a quarter turn and see if the secondary mirror reflec-
tion has moved closer to the center of the primary. If it moved
farther away then try loosening the same collimation knob a
bit. Repeat this process on the other two sets of collimation
screws, if necessary, adjusting them one way or the other and
seeing if the secondary mirror reflection moves closer to the
center of the primary mirror reflection. It will take a little trial
and error to get a feel for how to tilt the mirror in this way. When
the center hole in your collimating tool is centered as much as
possible on the reflection of the adhesive dot on the primary
mirror, your primary mirror is collimated. The view through the
collimation cap should resemble Figure 17D. Then, very lightly
tighten the three locking thumbscrews so that the primary mir-
ror stays in that position. A simple star test will tell you whether
the optics are accurately collimated.
14
Collimation
knob
Locking
thumbscrew
Out of collimation
Figure 20. A star test will determine if the telescope's
optics are properly collimated.
Star-Testing the Telescope
When it is dark, point the telescope at a bright star and accu-
rately center it in the eyepiece's field of view. Slowly de-focus
the image with the focusing knob. If the telescope is correct-
ly collimated, the expanding disk should be a perfect circle
(Figure 20). If the image is unsymmetrical, the scope is out
of collimation. The dark shadow cast by the secondary mir-
ror 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 cor-
rections to the telescope's position in order to account for the
sky's apparent motion.
6. Care and Maintenance
If you give your telescope reasonable care, it will last a lifetime.
Store it in a clean, dry, dust free place, safe from rapid chang-
es in temperature and humidity. Do not store the telescope
outdoors, although storage in a garage or shed is OK. Small
components like eyepieces and other accessories should be
kept in a protective box or storage case. Keep the caps on the
front of the scope and on the focuser when it is not in use. For
maximum protection during storage, we recommend placing
the telescope in a case to prevent any dust and moisture from
accumulating on exposed surfaces.
The telescope requires very little mechanical maintenance.
The optical tube is made of steel and has a smooth painted
finish that is fairly scratch-resistant. If a scratch does appear
on the tube, it will not harm the telescope. If you wish, you may
apply some auto touch-up paint to the scratch. Smudges on
the tube can be wiped off with a soft cloth and a household
cleaner.
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
Collimated
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