Orion StarBlast Instruction Manual page 6

Once the secondary mirror is centered in the focuser draw-
tube, and the primary mirror reflection is centered in the
secondary mirror, the secondary mirror is properly aligned,
and no further adjustments to it should be needed.
Aligning the Primary Mirror
The final adjustment is made to the primary mirror. It will need
adjustment if, as in Figure 4d, the secondary mirror is cen-
tered in the focuser drawtube 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 collimating
cap) is off-center.
The tilt of the primary mirror is adjusted with the three large
knurled thumbscrews on the rear end of the optical tube (back
of the mirror cell) (Figure 8). The small thumbscrews (with
slots in them) serve to lock the mirror in place. Start by loos-
ening each of these smaller thumbscrews a few turns. Use a
screwdriver in the slots, if necessary. Now adjust the tilt of the
primary mirror by turning one of the large thumbscrews either
clockwise or counterclockwise. Look into the focuser and see
if the secondary mirror reflection has moved closer to the
center of the primary mirror reflection. You can determine this
easily with the collimating cap and primary mirror center mark
by simply watching to see if the "dot" of the collimating cap is
moving closer or farther away from the "ring" on the primary
mirror. If it isn't getting closer, try turning the thumbscrew in
the opposite direction. Repeat this process for the other two
large thumbscrews, if necessary. It will take a little trial-and-
error to get the feel for how to adjust the primary mirror to
center the dot of the collimating cap in the ring of the primary
mirror center mark.
Figure 8.
The tilt of the primary mirror is adjusted by turning the
three larger thumbscrews.
When you have the dot centered as much as possible in the
ring, your primary mirror is aligned. The view through the colli-
mating cap should resemble Figure 4e. Make sure the smaller
thumbscrews on the back of the mirror cell are tightened to
lock the primary mirror in position.
6
A simple star test will tell you whether the optics are, in fact,
accurately aligned.
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 focus knob. If the telescope's optics are
correctly aligned, the expanding disk should be a perfect cir-
cle (Figure 9). If the image is unsymmetrical, the optics are
out of alignment. 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
optics are out of alignment.
If you try the star test and the bright star you have selected
is not accurately centered in the eyepiece, the telescope will
appear to need optical alignment, even though the optics may
be perfectly collimated. 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.
Out of collimation
Figure 9.
A star test will determine if the telescope's optics
are properly collimated. A defocused 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 alignment.
care & Maintenance
If you give your telescope reasonable care, it will last a life-
time. Store it in a clean, dry, dust-free place, safe from rapid
changes in temperature and humidity. Do not store the tele-
scope 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
dust cover on the front of the telescope and the dust cap on
the focuser drawtube when it is not in use.
Your StarBlast requires very little mechanical maintenance.
The optical tube 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 household cleaning fluid.
Collimated