ORION TELESCOPES & BINOCULARS Apex 9820 User manual

INSTRUCTION MANUAL
IN 161 Rev. C 02/09
Orion Apex™
Maksutov-Cassegrain Optical
Tube Assemblies
#9820 Apex 90mm #9823 Apex 102mm #9825 Apex 127mm
Corporate Offices: 89 Hangar Way, Watsonville CA 95076 - USA
Toll Free USA & Canada: [phone]
International: [phone]
Customer Support: [email protected]
Copyright © 2021 Orion Telescopes & Binoculars.All Rights Reserved. No part of this product instruction or any of its contents
may be reproduced, copied, modied or adapted, without the prior written consent of Orion Telescopes & Binoculars.
AN EMPLOYEE-OWNED COMPANY

Welcome to a new world of adventure! Your Apex
Maksutov-Cassegrain (Mak-Cass) telescope is
a ne-quality instrument designed for both day-
time terrestrial viewing and nighttime stargazing.
Compact, portable, and easy to use, this versatile
scope will provide many hours of enjoyment for the
whole family.
These instructions will help you set up and properly
use and care for your telescope. Please read them
over thoroughly before getting started.
Parts List
Qty. Description
1 Optical tube assembly
1 25mm Sirius Plössl eyepiece
1 45° correct-image diagonal
1 Correct-image nder scope
1 Finder scope bracket
1 Soft carry case
1 Optical tube dust cover
2
WARNING: Never look directly at the Sun
through your telescope or its nder scope—even
for an instant—without a professionally made
solar lter 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 1: The Apex Maksutov-Cassegrain optical tube assembly parts diagram. The Apex 102mm is shown,
but all models have similar components.
Eyepiece adapter
25mm Sirius
Plössl eyepiece
45° correct-image
diagonal
Focus knob
Mounting block
Meniscus lens
Correct-image nder scope
Dovetail holder
Finder scope
bracket

3
Getting Started
The Apex telescopes come nearly fully assembled from the
factory. The optics have been installed and collimated, so you
should not have to make any adjustments to them. Open the
box and inspect the contents to make sure all of the parts list-
ed above are present. Refer to Figure 1 to see what the parts
look like, and how they will connect togther; the Apex 102mm
is shown, but all models have similar components.
Please keep the original shipping box. In the unlikely event
you should need to ship the telescope back to Orion for war-
ranty repair service, you should use the original packaging.
The box also makes a very good container for storing the tele-
scope when it is not in use.
Installing the Accessories
Apex 90mm:
To place the nder scope in the nder scope bracket, rst
unthread the three alignment thumb screws on the bracket
until the screw ends are ush with the inside of the bracket’s
ring. Insert the nder scope into the bracket so that the eye-
piece end of the nder scope (the end with the rubber eye-
guard) is closest to the bracket’s alignment thumb screws
(see Figure 2). Secure the nder scope in place by tightening
the three alignment thumbscrews.
Apex 102mm and 127mm:
To place the nder scope in the nder scope bracket, rst
unthread the two black nylon alignment screws until the screw
ends are ush with the inside of the bracket’s cylinder. Place
the O-ring that comes on the base of the bracket over the
body of the nder scope until it seats into the slot on the mid-
dle of the nder scope. Insert the eyepiece end (narrow end)
of the nder scope into the end of the bracket’s cylinder that
does not have the alignment screws, while pulling the spring-
loaded tensioner on the bracket with your ngers (see Figure
3). Push the nder scope through the bracket until the O-ring
seats just inside the front opening of the bracket’s cylinder.
Now, release the tensioner and tighten the alignment screws
a couple of turns each to secure the nder scope in place.
All models:
Connect the nder scope bracket to the dovetail holder on
the optical tube with the thumb screw on the holder. Insert
the 45° diagonal into the eyepiece adapter and secure it with
the thumb screws on the eyepiece adapter. Insert an eye-
piece into the diagonal and tighten the thumb screws on the
diagonal.
Keep the dust cap over the front end of the telescope when it
is not in use. It is also a good idea to cover the eyepiece; use
the cover cap that came with it.
Mounting the Telescope on a Tripod
The Apex Maksutov-Cassegrain optical tube assemblies can
be mounted on any standard camera tripod that has a 1/4"-20
stud. The stud threads into the block on the underside of the
telescope’s optical tube (see Figure 4). Alternatively, the tele-
scopes can be attached to an altazimuth or equatorial mount
equipped with a 1/4"-20 adapter. For the Apex 127mm, there
are several threaded holes in the mounting block; use the one
that will best balance the telescope on the tripod or mount.
Figure 2: Insert the 6x20 nder scope into the bracket’s rings so
that it is oriented as shown.
Finder scope eyepiece
Figure 3: To install the 6x26 nder scope in the nder scope
bracket, pull the spring-loaded tensioner while inserting the
eyepiece end of the nder scope into the bracket.
Alignment thumb
screw (3)
Eyepiece end of
nder scope
Alignment thumb screws O-ring
Figure 4: The
1/4"-20 stud on
standard camera
tripods will thread
into the mounting
block on the
underside of the
Apex telescopes.
The Orion Paragon
HD-F2 tripod
shown utilizes a
quick-release shoe
to connect the
telescope to the
tripod.
1/4"-20 stud
Mounting block
Spring-loaded tensioner

4
Camera tripods or altazimuth mounts are desireable for ter-
restrial (land) viewing because they allow simple vertical and
horizontal movement of the telescope. An equatorial mount
is desirable for astronomical viewing because it allows easy
tracking of celestial objects as the Earth rotates. Also, the set-
ting circles on the mount enable you to locate objects by their
celestial coordinates (right ascension and declination), which
can be found in many observing books and star atlases.
Focusing
Point the telescope so the front end is aimed in the general
direction of an object you wish to view. When you rst look in
the eyepiece, the image you see may be fuzzy, or out of focus.
If so, gently turn the focus knob with your ngers 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.
Do You Wear Eyeglasses?
If you wear eyeglasses, you may be able to keep them on
while you observe, if your eyepieces have enough “eye relief”
to allow you to see the whole eld of view. You can nd out by
looking through the eyepiece rst with your glasses on and
then with them off, and see if the glasses restrict the view
to only a portion of the full eld. If they do, you can easily
observe with your glasses off by just refocusing the telescope
the needed amount.
If your eyes are astigmatic, images will probably appear the
best with glasses on. This is because a telescope’s focuser
can accommodate for nearsightedness or farsightedness,
but not astigmatism. If you have to wear your glasses while
observing and cannot see the entire eld of view, you may
want to purchase additional eyepieces that have longer eye
relief.
Aligning the Finder Scope
The Apex 90mm comes with a 6x20 correct-image finder
scope, while the Apex 102mm and 127mm both come with a
6x26 correct-image nder scope. (The rst number indicates
magnication, and the second number indicates the aperture
in millimeters.) The nder scope makes it easier to locate the
subject you want to observe in the telescope, because the
nder scope has a much wider eld of view. Unlike most nder
scopes, images viewed in the correct-image nder scope will
appear oriented the same as the naked eye, which makes
nding objects even easier. The 45° correct-image diagonal
provides a naked eye orientation for images in the main tele-
scope, so the view in the nder scope and main telescope will
be oriented the same, which is a great convenience.
Before you use the nder scope, it must be precisely aligned
with the telescope so they both point to exactly the same spot.
Alignment is easiest to do in daylight, rather than at night
under the stars. First, insert the 25mm eyepiece into the tele-
scope’s focuser. Then point the telescope at a discrete object
such as the top of a telephone pole or a street sign that is at
least a quarter-mile away. Position the telescope so the target
object appears in the very center of the eld of view when you
look into the eyepiece.
Now look through the nder scope. Is the object centered on
the nder scope’s crosshairs? If not, hopefully it will be visible
somewhere in the eld of view, so only ne adjustment of the
nder scope bracket’s alignment thumb screws will be need-
ed. Otherwise you’ll have to make coarser adjustments to
the alignment thumb screws to redirect the aim of the
nder scope.
Use the alignment thumb screws to center the object on the
crosshairs of the nder scope. Then look again into the tele-
scope’s eyepiece and see if it is still centered there too. If it
isn’t, repeat the entire process, making sure not to move the
telescope while adjusting the alignment of the nder scope.
Finder scopes can come out of alignment during transport of
the telescope, so check its alignment before each observing
session.
If, when looking through the nder scope, you notice that the
image is fuzzy, you will need to focus the nder scope for
your eyes. For the 6x20 nder scope of the Apex 90mm this is
done by rotating the nder’s eyepiece. For the 6x26 nder of
the Apex 102mm and 127mm, this is done by rst loosening
the lock ring that is located behind the nder’s objective lens
cell (see Figure 5). Once the lock ring is loosened, thread the
objective lens cell in or out until the image appears sharp.
Then, retighten the lock ring behind the lens cell. The nder
scope is now focused, and should not need focusing again for
your eyes.
Calculating Magnification (Power)
To calculate the magnication, or power, of a telescope with
an eyepiece, simply divide the focal length of the telescope by
the focal length of the eyepiece:
Magnification = telescope focal length ÷ eyepiece focal
length
For example, the Apex 102mm, which has a focal length of
1300mm, used in combination with the supplied 25mm eye-
piece, yields a power of:
1300 ÷ 25 = 52x.
It is desirable to have a range of eyepieces of different focal
lengths to allow viewing over a range of magnications. It is
not uncommon for an observer to own ve or more eyepieces.
Orion offers many different eyepieces of varying focal lengths,
so check the catalog or website for a wide selection of addi-
tional eyepieces to choose from.
Every telescope has a useful limit of power of about 2x per
millimeter of aperture (i.e. 204 x for the Apex 102mm). 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 dim-
mer and less sharp (this is a fundamental law of optics). The

5
steadiness of the air (the “seeing”) can also limit how much
magnication an image can tolerate.
Always start viewing with your lowest-power (longest focal
length) eyepiece in the telescope. It’s best to begin observ-
ing with the lowest-power eyepiece, because it will typically
provide the widest true eld of view, which will make nding
and centering objects much easier After you have located and
centered an object, you can try switching to a higher-power
eyepiece to ferret out more detail, if atmospheric conditions
permit. If the image you see is not crisp and steady, reduce
the magnication by switching to a longer focal length eye-
piece. 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, overmagnied image.
Terrestrial Viewing
For land viewing, it’s best to stick with low power eyepiec-
es that yield a magnication under 100x. At higher powers,
images rapidly lose sharpness and clarity due to “heat waves”
caused by Sun-heated air.
Remember to aim well clear of the Sun, unless the front of the
telescope is tted with a professionally made solar lter and
the nder scope is covered with foil or some other completely
opaque material.
The Apex telescopes are capable of focusing on objects that
are quite close, so you can view ne details of objects that are
nearby. Try focusing on a ower or insect at close distance to
enter a normally unseen microscopic world. Check the speci-
cations at the end of this manual for the closest focusing dis-
tance for each of the Apex models.
Astronomical Viewing
When choosing a location for nighttime stargazing, make it
as far away from city lights as possible. Light-polluted skies
greatly reduce what can be seen with the telescope. Also, give
your eyes at least 20 minutes to dark-adapt to the night sky.
You’ll be surprised at how many more stars you will see! Use
a red ashlight, to see what you’re doing at the telescope, or
to read star charts. Red light will not spoil your dark-adapted
night vision as readily as white light will.
To nd celestial objects with your telescope, you rst need
to become reasonably familiar with the night sky. Unless you
know how to recognize the constellation Orion, for instance,
you won’t have much luck locating the Orion Nebula. A simple
planisphere, or star wheel, can be a valuable tool for learn-
ing the constellations and seeing which ones are visible in the
sky on a given night. A good star chart or atlas, like the Orion
DeepMap 600, can come in handy for helping locate interest-
ing objects among the dizzying multitude of stars overhead.
Except for the Moon and the brighter planets, it is pretty time-
consuming and frustrating to hunt for objects randomly, with-
out knowing where to look. It is best to have specic targets in
mind before you begin looking through the eyepiece.
A. The Moon
The Moon, with its rocky, cratered surface, is one of the easi-
est and most interesting subjects to observe with your tele-
scope. The myriad craters, rilles, and jagged mountain forma-
tions offer endless fascination. The best time to observe the
Moon is during a partial phase, that is, when the Moon is not
full. During partial phases, shadows cast by crater walls and
mountain peaks along the border between the dark and light
portions of the lunar disk highlight the surface relief. A full
Moon is too bright and devoid of surface shadows to yield a
pleasing view. Try using a Moon lter to dim the Moon when it
is too bright; it simply threads onto the bottom of the eyepiece.
B.The Planets
The planets don’t stay put like stars do (planets don’t have
xed R.A. and Dec. coordinates), so you will have to refer
to Sky Calendar at our website, www.telescope.com, or to
charts published monthly in Astronomy, Sky & Telescope,
or other astronomy references to locate them. Venus, Mars,
Jupiter, and Saturn are the brightest objects in the sky after
the Sun and the Moon. All four of these planets are not nor-
mally visible in the sky at one time, but chances are one or
two of them will be.
JUPITER The largest planet, Jupiter, is a great subject to
observe. You can see the disk of the giant planet and watch
the ever-changing positions of its four largest moons, Io,
Callisto, Europa, and Ganymede. If atmospheric conditions
are good, you may be able to resolve thin cloud bands on the
planet’s disk.
SATURN The ringed planet is a breathtaking sight when it is
well positioned. The tilt angle of the rings varies over a period
of many years; sometimes they are seen edge-on, while at
other times they are broadside and look like giant “ears” on
each side of Saturn’s disk. A steady atmosphere (good see-
ing) is necessary for a good view.You may probably see a tiny,
bright “star” close by; that’s Saturn’s brightest moon, Titan.
VENUS At its brightest, Venus is the most luminous object in
the sky, excluding the Sun and the Moon. It is so bright that
sometimes it is visible to the naked eye during full daylight!
Ironically, Venus appears as a thin crescent, not a full disk,
when at its peak brightness. Because it is so close to the Sun,
it never wanders too far from the morning or evening horizon.
No surface markings can be seen on Venus, which is always
shrouded in dense clouds.
Focus
lock ring
Alignment
thumb screws
Spring-loaded
tensioner
Eyepiece
Objective lens
Figure 5. The 6x26 correct-image nder scope
and bracket.

6
MARS If atmospheric conditions are good, you may be able
to see some subtle surface detail on the Red Planet, possibly
even the polar ice cap. Mars makes a close approach to Earth
every two years; during those approaches its disk is larger
and thus more favorable for viewing.
C. Stars
Stars will appear like twinkling points of light in the telescope.
Even the largest telescopes cannot magnify stars to appear
as anything more than points of light. You can, however, enjoy
the different colors of the stars and locate many pretty double
and multiple stars. The famous “Double-Double” in the con-
stellation Lyra and the gorgeous two-color double star Albireo
in Cygnus are favorites. Defocusing the image of a star slightly
can help bring out its color.
D. Deep-Sky Objects
Under dark skies, you can observe a number of brighter
deep-sky objects with the Apex telescopes, including gaseous
nebulas, open and globular star clusters, and the brighter gal-
axies. Most deep-sky objects are very faint, so it is important
that you nd an observing site well away from light pollution.
Take plenty of time to let your eyes adjust to the darkness.
Don’t expect these objects to appear like the photographs
you see in books and magazines; most will look like dim gray
“ghosts.” (Our eyes are not sensitive enough to see color in
deep-sky objects except in few of the brightest ones.) But
as you become more experienced and your observing skills
improve, you will be able to coax out more and more intricate
details.
Photography
When coupled to a 35mm single-lens reex camera, the Apex
becomes a telephoto lens. For terrestrial or astronomical
photography, you need only a T-ring for your specic camera
model. The T-ring attaches to your camera and threads onto
the Apex’s eyepiece adapter (see Figure 6).
Use the camera’s viewnder to frame the picture. Use the tele-
scope’s focuser to focus the image. You may want to consider
using a remote shutter release instead of the shutter release
on the camera; touching the camera can vibrate the system
and blur the resulting photographic image on the lm. Also, be
sure to use a solid tripod.
If you would like to change the orientation of the camera rela-
tive to the telescope, do so by rst loosening the knurled ring
located in front of the eyepiece adapter (see Figure 6). You
can then rotate the camera (and eyepiece adapter) to the
desired orientation. Retighten the knurled ring when done.
Care & Maintenance
Transporting and Storing
The included soft carry case provides an excellent way to
transport and store the optical tube and its accessories. To
place the optical tube in the case, the eyepiece, diagonal,
nder scope and bracket must be removed from the tube.
When removing the eyepiece and diagonal, remember to
rst loosen the securing thumb screws. The nder scope and
bracket can be removed together by loosening the thumb
screw on the tube’s dovetail holder. Cover the front of the opti-
cal tube with the dust cover and the rear opening of the eye-
piece adapter with its cap. Now place the tube in the case’s
main compartment. The nder scope and bracket can also be
placed in the main compartment. Use the included removable
padded divider or padded tray to separate the nder scope
and bracket from the optical tube. The Apex 90mm and Apex
102mm come with one small padded divider and one padded
tray. The Apex 127mm comes with one padded tray only. The
padded tray will be on the bottom of the main compartment
of the case when it is shipped to you. For the Apex 90mm,
use the small divider to separate the nder scope and bracket
from the optical tube. For the Apex 102mm and Apex 127mm,
position the padded tray on top of the optical tube; the nder
scope and bracket can be stored on top of the tray so they will
not damage the tube. The eyepiece and diagonal should be
covered with their caps and placed in the external compart-
ments of the case.
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.
Cleaning the tube
Your Apex Maksutov-Cassegrain telescope requires very little
mechanical maintenance. The optical tube is aluminum and
has a smooth painted nish that is fairly scratch-resistant. If
a scratch does appear on the tube, it will not harm the tele-
scope. 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 such as Windex or Formula
409.
Cleaning Lenses
Any quality optical lens cleaning tissue and optical lens clean-
ing uid specically designed for multi-coated optics can be
used to clean the Apex’s front meniscus lens or exposed
lenses of your eyepieces or nder scope. Never use regular
glass cleaner or cleaning uid designed for eyeglasses. Before
cleaning with uid and tissue, however, blow any loose par-
ticles off the lens with a blower bulb or compressed air. Then
apply some cleaning uid to a tissue, never directly on the
optics. Wipe the lens gently in a circular motion, then remove
any excess uid with a fresh lens tissue. Oily ngerprints 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.
Figure 6: A T-ring
is all that is needed
to connect a 35mm
SLR camera to the
Apex telescopes;
it threads onto the
eyepiece adapter
with eyepiece and
diagonal removed.
Eyepiece adapter
T-ring
Knurled ring

7
Specifications
#9820 Apex 90mm OTA
Optical design: Maksutov-Cassegrain
Aperture: 90mm
Effective focal length: 1250mm
Focal ratio: f/13.9
Central obstruction diameter: 29mm
Primary mirror coating: Aluminum with overcoat
Meniscus lens coating: Anti-reection multi-coatings on both
sides of lens
Eyepiece adapter: Accepts 1.25” format accessories, camera
t-threads
Eyepiece: 25mm Sirius Plossl, fully coated with multi-coat-
ings, 1.25” format
Magnication with supplied eyepiece: 50x
Actual eld of view with supplied eyepiece: 0.96°
Diagonal: 45° correct-image diagonal, 1.25” format
Near focus (with supplied eyepiece and diagonal):
Approximately 13.5 feet
Finder scope: 6x magnication, 20mm aperture, correct-
image, achromatic, 6.2° eld
Optical tube mounting block: Fits standard photo-style tripods
Case: Deluxe carry case for optical tube included
Weight: 3.7 lbs
Length: 10.5” (without eyepiece or diagonal attached)
#9823 Apex 102mm OTA
Optical design: Maksutov-Cassegrain
Aperture: 102mm
Effective focal length: 1300mm
Focal ratio: f/12.7
Central obstruction diameter: 31mm
Primary mirror coating: Aluminum with overcoat
Meniscus lens coating: Anti-reection multi-coatings on both
sides of lens
Eyepiece adapter: Accepts 1.25” format accessories, camera
t-threads
Eyepiece: 25mm Sirius Plossl, fully coated with multi-coat-
ings, 1.25” format
Magnication with supplied eyepiece: 52x
Actual eld of view with supplied eyepiece: 0.92°
Diagonal: 45° correct-image diagonal, 1.25” format
Near focus (with supplied eyepiece and diagonal):
Approximately 11 feet
Finder scope: 6x magnication, 26mm aperture, correct-
image, achromatic, 6.3° eld
Optical tube mounting block: Fits standard photo-style tripods
Case: Deluxe carry case for optical tube included
Weight: 4.8 lbs
Length: 12.0” (without eyepiece or diagonal attached)
#9825 Apex 127mm OTA
Optical design: Maksutov-Cassegrain
Aperture: 127mm
Effective focal length: 1540mm
Focal ratio: f/12.1
Central obstruction diameter: 39mm
Primary mirror coating: Aluminum with overcoat
Meniscus lens coating: Anti-reection multi-coatings on both
sides of lens
Eyepiece adapter: Accepts 1.25” format accessories, camera
t-threads
Eyepiece: 25mm Sirius Plossl, fully coated with multi-coat-
ings, 1.25” format
Magnication with supplied eyepiece: 62x
Actual eld of view with supplied eyepiece: 0.77°
Diagonal: 45° correct-image diagonal, 1.25” format
Near focus (with supplied eyepiece and diagonal):
Approximately 27 feet
Finder scope: 6x magnication, 26mm aperture, correct-
image, achromatic, 6.3° eld
Optical tube mounting block: Fits standard photo-style tripods
Case: Deluxe carry case for optical tube included
Weight: 8.6 lbs
Length: 14.5” (without eyepiece or diagonal attached)

8
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Customer Support: [email protected]
Copyright © 2021 Orion Telescopes & Binoculars.All Rights Reserved. No part of this product instruction or any of its contents
may be reproduced, copied, modied or adapted, without the prior written consent of Orion Telescopes & Binoculars.
AN EMPLOYEE-OWNED COMPANY
One-Year Limited Warranty
This Orion product is warranted against defects in materials or workmanship for a period of one year from
the date of purchase. This warranty is for the benet of the original retail purchaser only. During this war-
ranty period Orion Telescopes & Binoculars will repair or replace, at Orion’s option, any warranted instru-
ment that proves to be defective, provided it is returned postage paid. Proof of purchase (such as a copy
of the original receipt) is required. This warranty is only valid in the country of purchase.
This warranty does not apply if, in Orion’s judgment, the instrument has been abused, mishandled, or
modied, nor does it apply to normal wear and tear. This warranty gives you specic legal rights. It is not
intended to remove or restrict your other legal rights under applicable local consumer law; your state or
national statutory consumer rights governing the sale of consumer goods remain fully applicable.
For further warranty information, please visit www.OrionTelescopes.com/warranty.