Orion 180mm Maksutov-Cassegrain User manual

INSTRUCTION MANUAL
IN 291 Rev. C 06/18
Providing Exceptional Consumer Optical Products Since 1975
Orion 180mm
Maksutov-Cassegrain
#9969 Optical Tube Assembly
OrionTelescopes.com
Customer Support: [phone]| E-mail: [email protected]
Corporate Offices: [phone], 89 Hangar Way, Watsonville, CA 95076
© 2008-2018 Orion Telescopes & Binoculars
Welcome to a new world of adventure! Your new
180mm Maksutov-Cassegrain (Mak-Cass) tele-
scope is a fine-quality instrument that excels for
high-power observing and solar system imaging.
These instructions will help you set up and properly
use and care for your telescope. Please read them
over thoroughly before getting started.
Getting Started
Your telescope comes fully assembled from the factory. The
optics have been installed and collimated, so you should not
have to make any adjustments to them. Keep the dust covers
on the telescope when it is not in use.
Please keep the original shipping box. In the unlikely event you
should need to ship the telescope back to Orion for warranty
repair service, you should use the original packaging. The box
also makes a very good container for storing the telescope.
The Orion 180mm Maksutov-Cassegrain has been upgraded to
now include a 2"visual back with 1.25"adapter (Figure 1),
allowing use of either 2"or 1.25"diagonals, eyepieces, and
accessories (all sold separately). In addition, the 2"visual back
can be removed to expose an SCT-threaded collar (2" x 24)
TPI. This would accommodate SCT-specific accessories such
as a thread-on diagonal or various camera adapters.
The 180mm Maksutov-Cassegrain comes equipped with
a Vixen-style dovetail mounting plate for attachment of the
optical tube to a compatible telescope mount. In addition,
the optical tube is outfitted with a dovetail finder scope base,
which accepts any Orion finder scope or reflex sight.

2
Focusing
You will find the helical focus knob next to the visual back on
the back end of the optical tube. Rotate the rubber-covered
knob to change the focus. It operates by sliding the primary
mirror inside the telescope incrementally forward or backward.
Point the telescope so the front end is aimed in the general
direction of an object you wish to view. When you first look in
the eyepiece, the image you see may be fuzzy, or out of focus.
If so, gently turn the focus knob with your fingers until the
image becomes sharp. Go a little bit beyond sharp focus until
the image just starts to blur again, then reverse the rotation of
the knob, just to make sure you’ve hit the exact focus point.
You will have to readjust the focus when aiming at subjects of
varying distances, or after changing eyepieces.
If you have trouble focusing, rotate the focus knob counter-
clockwise as far as it will go. Now look through the eyepiece
while slowly rotating the focus knob clockwise. You should
soon see the point at which focus is reached.
Calculating Magnification
To calculate the magnification, or power, of a telescope with an
eyepiece, simply divide the focal length of the telescope by the
focal length of the eyepiece:
Telescope Focal Length (mm)
= Magnification
Eyepiece Focal Length (mm)
For example, the 180mm Maksutov-Cassegrain, which has
a focal length of 2700mm, used in combination with a 25mm
eyepiece, yields a magnification of:
2700 mm
= 108x
25 mm
It is desirable to have a range of eyepieces of different focal
lengths to allow viewing over a range of magnifications. It is
not uncommon for an observer to own five or more eyepieces.
Orion offers many different eyepieces of varying focal lengths,
so check the catalog or www.OrionTelescopes.com for a wide
selection of additional eyepieces to choose from.
Every telescope has a useful limit of power of about 2x per mil-
limeter of aperture (i.e. 360x for the 180mm Mak-Cass). Claims
of higher power by some telescope manufacturers are a mis-
leading advertising gimmick and should be dismissed. Keep in
mind that at higher powers, an image will always be dimmer
and less sharp (this is a fundamental law of optics). The steadi-
ness of the air (the “seeing”) can also limit how much magnifi-
cation an image can tolerate.
Always start viewing with your lowest-power (longest focal
length) eyepiece in the telescope. It’s best to begin observing
with the lowest-power eyepiece, because it will typically pro-
vide the widest true field of view, which will make finding and
centering objects much easier. After you have located and cen-
tered an object, you can try switching to a higher-power eye-
piece to ferret out more detail, if atmospheric conditions permit.
If the image you see is not crisp and steady, reduce the mag-
nification by switching to a longer focal length eyepiece. As a
general rule, a small but well-resolved image will show more
detail and provide a more enjoyable view than a dim and fuzzy,
over-magnified image.
Photography
For photography with the 180mm Maksutov-Cassegrain, you
can use a DSLR or any of a wide variety of astronomical CCD
or CMOS cameras. For DSLRs you will need a T-ring for your
particular camera as well as a camera adapter with a 2"nose-
piece to couple the camera to the telescope. Larger astronomi-
cal cameras may already be equipped with a 2"nosepiece; if
not you will need to purchase a 2"T-adapter. Smaller “plan-
etary” cameras often have a 1.25"barrel, which you can insert
Finder
scope base
2" Visual back
1.25" adapter
Focus knob
Mounting bar
Tapped holes for
optional finder
scope base
Figure 1. Key parts of the 180m Maksutov-Cassegrain.

3
Out of collimation Collimated
Out of
Collimation
Collimated
Out of collimation Collimated
directly into the 1.25"adapter that comes with the 180mm
Maksutov-Cassegrain.
Care & Maintenance
If you give your telescope reasonable care, it will last a lifetime.
When not in use, keep the dust cover on the front of the tube
and the dust cap on the eyepiece adapter. Store it in a clean,
dry, dust-free place, safe from rapid changes in temperature
and humidity. Do not store the telescope outdoors, although
storage in a garage or shed is OK.
Your telescope requires very little mechanical maintenance.
The optical tube is aluminum 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 household cleaning fluid.
Any quality optical lens cleaning tissue and optical lens cleaning
fluid specifically designed for multi-coated optics can be used
to clean the front meniscus lens of the telescope. Never use
regular glass cleaner or cleaning fluid designed for eyeglass-
es. Before cleaning with fluid and tissue, however, 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, 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. For the large surface of the meniscus lens,
clean only a small area at a time, using a fresh lens tissue on
each area. Never reuse tissues.
Appendix: Collimation
Collimating is the process of aligning a telescope’s optics. Your
Maksutov-Cassegrain's primary mirror was aligned at the fac-
tory and should not need adjustment unless the telescope is
handled roughly. This manual contains information on how to
test the collimation of your telescope and instructions for prop-
er alignment should that be needed.
Star-Testing the Telescope
Before you start adjusting the primary mirror of your telescope,
make certain that it is actually out of collimation by performing
a star test.
Take your telescope out at dusk and let it acclimate to the out-
side temperature; this usually takes 30-60 minutes. When it is
dark, point the telescope upwards 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 correctly
collimated, the expanding disk should be a circle (Figure 2).
If the image is unsymmetrical, the scope is out of collimation.
Also, 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 but 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.
Collimating
To collimate your telescope, remove the diagonal and eyepiece
and look into the rear opening of the tube (also remove the dust
cover from the front of the tube). This should be done indoors,
with the telescope pointed at a white wall in a well-lit room.
Try to keep your eye centered with respect to the rear open-
ing of the tube as best as possible. Using an Orion Collimating
Eyepiece will aid greatly in keeping your eye centered and is
strongly recommended.
Alternatively, you can make a crude collimating tool out of an
empty, black plastic 35mm film canister. It will not have cross-
hairs, so it won’t be as precise, but it will be better than nothing.
Cut 1⁄2" from the top lip of the canister and put a 1/16" to 1/8"
diameter hole in the center of the canister’s bottom surface.
Insert the film canister collimating tool into the focuser like you
would an eyepiece with the bottom surface outward.
Once you are ready to collimate, look into the rear opening of
the tube. If your telescope is out of collimation, it will resemble
Figure 3a. You will see a reflection of the inside of the optical
tube resembling a black crescent. A properly collimated scope
WARNING: Never look directly at the Sun through
your telescope—even for an instant—without a
professionally made solar filter that completely
covers the front of the instrument, or permanent
eye damage could result. Young children should
use this telescope only with adult supervision.
Figure 2. A star test will determine if a telescope’s optics are
properly collimated. An unfocused view of a bright star through the
eyepiece should appear as illustrated on right if optics are perfectly
collimated. If circle is unsymmetrical, as in illustration on left, scope
needs collimation.

4
will resemble Figure 3b. The direction of misalignment in
your telescope may differ from Figure 3a, but the diagram will
give you a general idea of how things will look.
Note there are three pairs of collimation screws on the back
of the optical tube (Figure 4). The tilt of the primary mirror
is adjusted with the three pairs of collimation screws. You will
need a 4mm and 2.5mm hex key to turn these screws.
Each pair of collimation screws work together to adjust the tilt
of the primary mirror. One screw pushes the mirror cell forward,
while the other screw pulls the mirror cell back. One must be
loosened and the other tightened by equal amounts in order
to adjust the tilt. Look into the rear opening of the tube and
locate the black crescent that indicates the optics are out of
collimation. Note which way the front of the telescope would
need to move in order to “fill” that black crescent and resemble
Figure 3b. Then look at the back end of the telescope and
locate the pair of collimation screws that are in the direction
that the front of the telescope needs to move. Tighten one of
these screws by one turn, and loosen the other screw of the
pair by one turn. Look into the rear opening of the tube and
determine if the black crescent has reduced in size, increased
in size, or been “filled.” If the crescent has reduced in size,
continue adjusting the pair of collimation screws in the same
manner until the crescent has been completely “filled.” If the
crescent has increased in size, the optics have been moved
further out of alignment. To correct this, loosen and tighten the
same pair of collimation screws by one turn to undo the previ-
ous adjustment. Then adjust the other two pairs of collimation
screws until the black crescent is “filled.”
It will take a little trial and error to get a feel for how to tilt the
mirror using the collimation screw pairs. Again, collimation
should only be attempted if you have confirmed the telescope
is actually out of collimation by performing a star test.
Finishing Collimation
Once you have finished adjusting your telescope, you will need
to perform another star test (described earlier) to check the col-
limation. If your telescope appears collimated after star test-
ing, it should not need adjustment again unless it is roughly
handled.
If you have gone through this process and your telescope is
still out of collimation, please contact Orion customer support.
You may need to return the telescope for repair (covered on
warranty for 1 year after purchase).
Figure 4. The 180mm Maksutov-Cassegrain collimation screws
Collimation
screw pairs
Figure 3. a) If the telescope’s optics are out of alignment the view
through rear opening of the telescope will resemble this.
b) With the optics properly aligned the view through the rear
opening of the telescope will resemble this.
Front of
telescope
Secondary
mirror
Reflection of your eye
in secondary mirror
Reflection of
inside of tube
(misalignment)
Secondary
reflection of
inside of tube
a
Front of
telescope
Secondary
mirror
Reflection of your eye
in secondary mirror
b

5
Specifications
Optical design: Maksutov-Cassegrain
Aperture: 180mm
Effective focal length: 2700mm
Focal ratio: f/15.0
Central obstruction
diameter: 41mm
Primary mirror coating: Aluminum with SiO2 overcoat
Meniscus lens coating: Anti-reflection multi-coatings on
both sides of lens
Visual back: 2" with 1.25" adapter
Mounting plate: Vixen style dovetail bar
Weight: 16 lbs.

6
This page left blank intentionally.

7
This page left blank intentionally.

8
One-Year Limited Warranty
This Orion 180mm Maksutov-Cassegrain Telescope is warranted against defects in materials or work-
manship for a period of one year from the date of purchase. This warranty is for the benefit of the
original retail purchaser only. During this warranty period Orion Telescopes & Binoculars will repair or
replace, at Orion’s option, any warranted instrument that proves to be defective, provided it is returned
postage paid to: Orion Warranty Repair, 89 Hangar Way, Watsonville, CA 95076. If the product is not
registered, proof of purchase (such as a copy of the original invoice) is required.
This warranty does not apply if, in Orion’s judgment, the instrument has been abused, mishandled, or
modified, nor does it apply to normal wear and tear. This warranty gives you specific legal rights, and
you may also have other rights, which vary from state to state. For further warranty service information,
contact: Customer Service Department, Orion Telescopes & Binoculars, P. O. Box 1815, Santa Cruz,
CA 95061; (800)-676-1343.
Orion Telescopes & Binoculars
Post Office Box 1815, Santa Cruz, CA 95061
Customer Support Help Line (800)-676-1343 • Day or Evening