Page 1
INSTRUCTION MANUAL
Orion® 3.6"
Clear-Aperture Reflector
Optical Tube Assembly
Primary mirror cell
#9768
Dovetail mount Focuser
Focus knobs
Secondary mirror
holder
Figure 1. The 3.6" Clear-Aperture reflector optical tube assembly.
Congratulations on your purchase of an Orion telescope. Your new 3.6" Clear-Aperture (CA) reflector is
specifically designed for high-resolution visual observation of astronomical objects. With its unobstructed
optical system, you’ll be able to enjoy razor sharp views of objects such as planets, the Moon, double
stars, and hundreds of other fascinating celestial denizens.
About the Clear-Aperture Newtonian
Optical Design
The clear-aperture Newtonian is an exciting optical design that
has gained popularity in recent years. Because of its unobstructed primary mirror, it provides much higher image contrast
than obstructed optical designs, such as standard Newtonians
and Schmidt-Cassegrains. The secondary mirrors in those
types of telescopes block a significant portion of the incoming
light, which only serves to reduce image contrast.
In addition, since the incoming light does not pass through any
lenses, there is no chromatic aberration (color dispersion) in
clear-aperture Newtonians, as is present in refractors. In fact,
side-by-side testing shows clear-aperture Newtonians can
out perform apochromatic refractors of similar aperture that
cost over twice as much! This is because the clear-aperture
Newtonian has absolutely no chromatic aberration to speak of.
Even the most expensive apochromatic refractors have some
residual chromatic aberration, which reduces image contrast.
As a result, the SkyView Pro 3.6 CA EQ yields incredibly highcontrast images. Expect to see amazingly crisp views of the
planets, Moon, Sun (with optional solar filter, of course!), double stars, and bright star clusters.
WARNING: Never look directly at the Sun
through your telescope or its finder scope—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.
IN 242 REV A 10/04
Page 2
Getting Started
The telescope will arrive in one box. We recommend keeping the box and all original packaging. In case the telescope
needs to be shipped to another location, or returned to Orion
for warranty repair, having the proper box and packaging will
help ensure your telescope will survive the journey intact. The
box also makes a good container for storing the telescope
when not in use.
In addition to the optical tube assembly, you will find a collimation cap, rear cover plate, and two cover plate thumbscrews.
Dust covers for the front opening of the tube and for the
focuser drawtube are also included.
Installing the Rear Cover Plate
The rear cover plate reduces the amount of light that can enter
the telescope from behind the mirror cell, which improves
image contrast. It can be removed prior to observing to facilitate rapid cooling of the primary mirror, which ensures the
best views through the telescope. To install the rear cover
plate (if not already on the mirror cell), simply line up the small
holes in the cover plate with two of the four threaded holes in
the rear of the mirror cell. Then, thread the cover plate thumbscrews through the cover plate and into the rear of the mirror
cell (Figure 2). The larger hole in the center of the cover plate
is a finger hole to make it easier to remove the plate.
Figure 2. Thread the cover plate thumbscrews through the rear
cover plate and into two of the threaded holes in the back of the
mirror cell.
Connecting to a Mount
Optional tube rings should be used to attach the scope to a
telescope mount. Tube rings with an inner diameter of 182mm
(7.2"), such as Orion item #7375, are needed.
Use of Optional Eyepieces and Finder Scope
The 3.6" CA reflector does not come with a finder scope or
eyepieces in order to grant the user the greatest versatility in
customizing the instrument to suit their needs.
Any Orion finder scope with a dovetail bracket can be used
with the 3.6" CA reflector. Simply unthread the thumbscrew on
the tube’s dovetail mount (Figure 1) and insert the assembled
finder scope and dovetail bracket. Then retighten the thumbscrew. Finder scope brackets that do not match the dovetail
mount will need to be attached by some other means.
The 3.6" CA reflector can use almost any 1.25" eyepiece.
Remove the cover cap from the focuser drawtube, loosen
the two thumbscrews, and insert the eyepiece. Secure the
eyepiece with the thumbscrews on the drawtube. Focus the
telescope by rotating one of the focus knobs.
Magnification & Eyepieces
Magnification, or power, is determined by the focal length of
the telescope and the focal length of the eyepiece. Therefore,
by using eyepieces of different focal lengths, the resultant
magnification can be varied.
Magnification is calculated as follows:
Telescope Focal Length (mm)
Eyepiece Focal Length (mm)
= Magnification
The 3.6" CA reflector has a focal length of 1240mm, so when
used with a 25mm eyepiece yields:
1240 mm
= 50x
25 mm
The magnification provided by a 10mm eyepiece is:
1240 mm
= 124x
10 mm
The maximum attainable magnification for a telescope is
directly related to how much light it can gather. The larger the
aperture, the more magnification is possible. In general, a figure of 50x per inch of aperture is the maximum attainable for
most telescopes. Your 3.6" CA reflector has an aperture of 3.6
inches, so the maximum magnification would be about 180x.
This level of magnification assumes you have ideal conditions
for viewing.
Keep in mind that as you increase magnification, the brightness of the object viewed will decrease; this is an inherent
principle of the laws of physics and cannot be avoided. If
magnification is doubled, an image appears four times dimmer. If magnification is tripled, image brightness is reduced
by a factor of nine!
It is quite common for an observer to own five or more eyepieces to access a wide range of magnifications. This allows
the observer to choose the best eyepiece to use depending
on the object being viewed.
Whatever you choose to view, always start by inserting your
lowest power (longest focal length) eyepiece to locate and
center the object. Low magnification yields a wide field of
view, which shows a larger area of sky in the eyepiece. This
makes acquiring and centering an object much easier. If you
try to find and center objects with high power (narrow field of
view), it’s like trying to find a needle in a haystack!
2
Page 3
Once you’ve centered the object in the eyepiece, you can
switch to higher magnification (shorter focal length eyepiece),
if you wish. This is especially recommended for small and
bright objects, like planets and double stars. The Moon also
takes higher magnifications well.
Deep-sky objects, however, typically look better at medium
or low magnifications. This is because many of them are
quite faint, yet have some extent (apparent width). Deep-sky
objects will often disappear at higher magnifications, since
greater magnification inherently yields dimmer images. This
is not the case for all deep-sky objects, however. Many galaxies are quite small, yet are somewhat bright, so higher power
may show more detail.
The best rule of thumb with eyepiece selection is to start
with a low power, wide field, and then work your way up in
magnification. If the object looks better, try an even higher
magnification. If the object looks worse, then back off the
magnification a little by using a lower power eyepiece.
Focuser Adjustments
The metal thumbscrew on the top of the body of the focuser
(Figure 3) will lock the focuser drawtube in place once the
telescope is properly focused. Before focusing with the focus
knob, remember to first loosen this thumbscrew. Do not loosen the thumbscrew too much as there must be some tension
to keep the drawtube secure within the focuser.
If you find the drawtube tension when focusing is either too
tight (focus knobs are difficult to turn) or too loose (image
shifts when focusing), you can adjust it by tightening or loosening the two drawtube tensioning setscrews on the focuser.
These are the two small setscrews located on either side of
the focus lock thumbscrew (Figure 3). Adjusting these setscrews requires a 1.5mm hex key.
Drawtube tensioning
setscrews
Focus lock
thumbscrew
Figure 3. The large thumbscrew on the focuser locks the
drawtube position. The two small setscrews adjust the tension of
the focuser drawtube.
Collimating (Aligning the Mirrors)
Collimating is the process of adjusting the mirrors so they
are precisely aligned with each another and the telescope’s
focuser. Your telescope’s optics were aligned at the factory,
and should not need much adjustment unless the telescope
is handled roughly. Accurate mirror alignment is important to
ensure peak performance of your telescope, so it should be
checked regularly. Collimating is relatively easy to do and can
be done in daylight, although a final “tweak” under the stars
may improve performance somewhat.
A. The Collimation Cap and Mirror Center Mark
Your 3.6" CA reflector comes with a collimation cap. This is a
simple cap that fits on the focuser drawtube like a dust cap,
but has a small hole in the center. This helps center your eye
so that collimating is easier to perform.
In addition to the collimation cap, the primary mirror is marked
with a black spot at its exact center. This “center mark” helps
to achieve a precise optical alignment, as you don’t have to
guess where the center of the primary mirror is. The center mark is also required for best results when using other
collimating devices, such as Orion’s LaserMate Collimator,
obviating the need to remove the primary mirror and mark it
yourself.
B. Aligning the Secondary Mirror
To check alignment of the secondary mirror (the small mirror
held diagonally at the front of the tube), remove the eyepiece
and look down the focuser drawtube. You should see the secondary mirror centered in the drawtube and the reflection of
the primary mirror centered in the secondary mirror, as in
Figure 4a. If anything is off-center, as in Figure 4b, you will
need to align the secondary mirror.
It helps to adjust the mirrors in a brightly lit room with the telescope pointed towards a bright surface, such as white paper
or wall. Placing a piece of white paper in the telescope tube
opposite the focuser and behind the secondary mirror will also
be helpful in determining the outline of the secondary mirror
itself. The telescope tube should be oriented horizontally, as
this prevents any parts from the secondary mirror assembly
from falling down onto the primary mirror should something
come loose.
With the collimation cap on the focuser drawtube, look
through the hole in the cap at the secondary mirror. Ignore the
reflections within the secondary mirror for the time being. The
secondary mirror itself should be centered in the collimation
cap. If it isn’t, as in Figure 4b, its position must be adjusted.
This adjustment should rarely need to be done.
To center the secondary mirror in the focuser drawtube in the
direction perpendicular to the optical axis (i.e. up-and-down in
the collimation cap), you will need to loosen the two Phillips
head screws that secure the secondary mirror holder to the
tube. Move the entire secondary mirror holder within the slots
until the mirror is centered up-and-down in the collimation cap
(Figure 5a). Retighten the Phillips head screws.
To center the secondary mirror in the collimation cap in the
direction parallel to the optical axis of the telescope (i.e. leftand-right in the collimation cap), use a 2mm hex key to loosen
3
Page 4
Primary mirror
center mark
a.
Figure 5a.
To adjust the
secondary mirror
position up and
down in the
collimation cap,
loosen the two
Phillips head screws
that attach the entire
secondary mirror
holder to the tube,
and move the mirror
holder in the slots.
b.
d.
c.
e.
Figure 4. Collimating the optics. (a) When the mirrors are properly
aligned, the view down the focuser drawtube should look like this (b)
With the collimation cap in place, if the optics are out of alignment, the
view might look something like this. (c) Here, the secondary mirror is
centered in the collimation cap, but it needs to be adjusted (tilted) so
that the entire primary mirror is visible. (d) With the collimation target
on the front of the tube, the secondary mirror is correctly aligned, but
the primary mirror still needs adjustment. When the primary mirror
is correctly aligned, the target's center will coincide with the primary
mirror center mark, as in (e).
the three small alignment setscrews in the center hub of the
secondary mirror holder several turns. Now keep the mirror
stationary (be careful not to touch the surface of the mirror!),
while turning the center screw with a Phillips head screwdriver
(Figure 5b). Turning the screw clockwise will move the secondary mirror toward the front opening of the optical tube (to the
left in the collimation cap), while turning the screw counterclockwise will move the secondary mirror toward the primary
mirror (to the right in the collimation cap). When the secondary mirror is best centered in the collimation cap, rotate the
secondary mirror until the reflection of the primary mirror is
Figure 5b. To adjust the secondary mirror position left and right
in the collimation cap, loosen or tighten the Phillips head screw
in the center of the mirror holder, while holding the mirror itself
stationary.
as centered in the secondary mirror as possible. It may not be
perfectly centered, but that is OK for now. Tighten the three
small alignment screws equally to secure the secondary mirror in that position.
If the entire primary mirror reflection is not visible in the secondary mirror, as in Figure 4c; you will need to adjust the tilt
of the secondary mirror. This is done by alternately loosening
one of the secondary mirror holder’s three alignment setscrews while tightening the other two, as depicted in Figure
6. The goal is to center the primary mirror reflection in the
secondary mirror, as in Figure 4d. The primary mirror center
mark greatly aids in doing this.
Once the secondary mirror itself and the reflection of the primary mirror (and center mark) are centered in the collimation
cap, the secondary mirror is collimated.
4
Page 5
Figure 6. The tilt of the secondary mirror is adjusted by
alternately tightening and loosening the three alignment setscrews
in the mirror holder.
C. Aligning the Primary Mirror
The final adjustment is made to the tilt of the primary mirror. To
perform this adjustment properly, you will need to make a collimation target for the front opening of the telescope tube. This
can be done by placing the telescope’s dust cover on a piece
of paper and tracing the dust cover’s outline. Make the outline
a circle; do not trace the dust cover’s removal tabs. Cut the
circle out, and precisely fold it in half. Then fold the half-circle
precisely in half again, to create precise quarter circles. Unfold
the circle, and mark the intersection of the folds with a black
pen; this is the precise center of the target. Center the target
on the front opening of the telescope, and tape it onto the tube
so it is secure (Figure 7).
The tilt of the primary mirror is adjusted with three springloaded collimation thumbscrews on the back end of the optical
tube (bottom of the primary mirror cell); these are the larger
thumbscrews. The other three smaller thumbscrews lock the
mirror’s position in place; these thumbscrews must be loosened before any collimation adjustments can be made to the
primary mirror.
To start, turn the smaller thumbscrews that lock the primary
mirror in place a few turns each (Figure 8). Use a screwdriver
in the slots, if necessary.
Figure 8. The three small thumbscrews that lock the primary
mirror in place must first be loosened before any adjustments can be
made. A flat head screwdriver may be used to loosen these screws.
Fold lines
Figure 7. To collimate the primary mirror, make a collimation
target and center it on the front opening of the optical tube. Tape the
target onto the tube.
Now, look into the collimation cap, and note the center spot on
the collimation target within the reflection of the primary mirror. If the target’s center spot lies directly on the primary mirror
center mark, the primary mirror is already aligned. If not, as in
Figure 4d, the tilt of the primary mirror will need adjustment until
the target and the primary mirror centers coincide.
Now try tightening or loosening one of the larger collimation
thumbscrews with your fingers (Figure 9). Look into the collimation cap and see if the target’s center has moved closer
to the primary mirror’s center. Continue making adjustments
to the thumbscrews until the target’s center spot lies directly
on the primary mirror center mark, as in Figure 4e. When this
is accomplished, your primary mirror is collimated. Re-tighten
the primary mirror locking thumbscrews, and remove the collimation target from the front of the tube.
A simple star test will tell you whether the optics are, in fact,
accurately aligned with each other and the focuser. This is
recommended, as some slight “tweaks” to the telescope’s collimation may be needed for optimal performance.
5
Page 6
Figure 9. The tilt of the primary mirror is adjusted by turning one
Out of collimation Collimated
or more of the three larger thumbscrews.
D. Using an Optional Laser Collimator
Optional laser collimators, like the Orion LaserMate, can greatly aid in aligning the 3.6" CA reflector’s optics. Laser collimators
only help to adjust the tilt of the mirrors, so centering the secondary mirror must be done with the collimation cap. Use the
procedure described previously to do this. Once the secondary
mirror itself is accurately centered in the collimation cap, use
the following procedure to adjust the tilt of both mirrors:
1. Place the laser collimator into the focuser drawtube, and
secure it with the thumbscrews on the drawtube.
2. Turn the laser pointer on.
3. Hold a white sheet of paper over the front of the telescope
to determine where the exiting laser beam is currently positioned. Avoid placing your eye in this area while making
collimation adjustments. Remove the sheet of paper.
4. Look down the tube, and see where the laser beam reflects
off the primary mirror. This reflection will appear as a red
spot on the primary mirror (or somewhere else within the
tube if the secondary mirror tilt is very misaligned). Make
adjustments to the three setscrews that adjust the tilt of the
secondary mirror (Figure 6) until the laser spot is centered
on the primary mirror’s center mark. The secondary mirror
is now collimated.
5. To adjust the tilt of the primary mirror, you will need to make
a collimation target for the front opening of the telescope
tube. This can be done by placing the telescope’s dust
cover on a piece of paper and tracing the dust cover’s outline. Make the outline a circle; do not trace the dust cover’s
removal tabs. Cut the circle out, and precisely fold it in half.
Then fold the half-circle precisely in half again, to create
precise quarter circles. Unfold the circle, and mark the
intersection of the folds with a black pen; this is the precise
center of the target.
6. Center the target on the front opening of the telescope, and
tape it onto the tube so it is secure (Figure 7).
7. Unlock the three primary mirror lock thumbscrews (Figure
8), and use the three primary mirror collimation thumbscrews (Figure 9) to center the exiting laser beam onto the
center of the target.
8. Retighten the primary mirror lock thumbscrews, and
remove the target from the tube. The primary mirror is now
collimated.
A simple star test will tell you whether the optics are, in fact,
accurately aligned with each other and the focuser. This is
recommended, as some slight “tweaks” to the telescope’s collimation may be needed for optimal performance.
E. Star-Testing the Telescope
When it is dark, point the telescope at a bright star and accurately center it in the 10mm eyepiece’s field of view. Slowly
defocus the image with the focusing knob. If the telescope is
accurately collimated, the expanding disk should be a circle
(Figure 10). If the image is unsymmetrical (i.e. oblong or oval),
the telescope is somewhat out of collimation.
Figure 10. 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 the right if the optics
are perfectly collimated. If the circle is unsymmetrical, as in the
illustration on the left, the scope needs collimation.
If you try the star test and the bright star you have selected is
not 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.
For clear-aperture Newtonians, such as the 3.6" CA reflector,
collimation errors produce astigmatism in the optical system.
If you believe your telescope’s mirrors are collimated, yet outof-focus star images still appear slightly oblong, you may need
to “tweak” the collimation of the primary mirror slightly. Do this
by only adjusting the primary mirror collimation thumbscrew
that is in line with the focuser (Figure 11). Loosen the three
collimation lock thumbscrews (Figure 8) and turn the in line
collimation thumbscrew approximately one-quarter turn clockwise or counterclockwise, re-center the star in the eyepiece,
and perform the star test again. Continue making small adjustments to this thumbscrew only until the star appears round
when defocusing. Retighten the collimation lock thumbscrews
when done.
6
Page 7
Precisely collimating a clear-aperture Newtonian telescope
can be a bit confusing and time consuming at first, but is necessary to get the best possible optical performance. Once the
telescope is collimated, the mirrors should not need much
adjustment again unless roughly handled or jostled.
Figure 11. If star test
images are not perfectly
round even though you
believe the telescope
to be well collimated,
try slightly tightening or
loosening the primary
mirror collimation
thumbscrew that is in
line with the telescope's
focuser.
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 changes 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 dust cover
on the front of the telescope and the dust cap on the focuser
drawtube when not in use.
Your 3.6" CA reflector requires very little mechanical maintenance. The optical tube is 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. Smudges on the tube can be
wiped off with a soft cloth and a household cleaning fluid.
Cleaning Mirrors
You should not have to clean the telescope’s mirrors very often;
normally once every year or so. Covering the telescope with its
dust covers when it is not in use will prevent dust from accumulating on the mirrors. Improper cleaning can scratch mirror
coatings, so the fewer times you have to clean the mirrors, the
better. Small specks of dust or flecks of paint have virtually no
effect on the performance of the telescope.
The primary mirror and the secondary mirror of the 3.6" CA
reflector are front-surface aluminized (enhanced 96% reflective for primary) and over-coated, which prevents the aluminum
from oxidizing. These coatings normally last through many
years of use before requiring re-coating, which is easily done.
To clean the secondary mirror, it must be removed from the
telescope. Do this by holding the secondary mirror holder
stationary while turning the center Phillips-head screw counterclockwise. Be careful, there is a spring between the secondary
mirror holder and the Philips-head screw; be sure that it will
not fall into the optical tube and hit the primary mirror. Handle
the mirror by its holder; do not touch the mirror surface. Then
follow the same procedure described below for cleaning the
primary mirror. You do not need to remove the secondary mirror from its holder when cleaning.
To clean the primary mirror, carefully remove the mirror cell
from the telescope. Do this by removing the four screws on the
end of the tube that secure the primary mirror cell. Now, remove
the entire mirror cell from the tube. Completely unthread the
three large primary mirror collimation thumbscrews (actually
thumbnuts) from the primary mirror cell. The inner part of the
cell containing the primary mirror is now free from the cell’s
rear end ring. The primary mirror will be cleaned attached to
the inner part of its cell, as it is permanently attached with silicone adhesive.
Lift the mirror cell carefully, do not touch the surface of the mirror with your fingers. Set the mirror (in its cell) on a clean, soft
towel. Fill a clean sink free of abrasive cleanser, with room-temperature water, a few drops of liquid dishwashing detergent,
and if possible, a capful of 100% isopropyl alcohol. Submerge
the mirror and cell (aluminized face up) in the water and let
it soak for a few minutes (or hours if it’s a very dirty mirror).
Wipe the mirror surface under water with clean cotton balls,
using extremely light pressure and stroking in straight lines
across the mirror. Use one ball for each wipe across the mirror.
Then rinse the mirror under a stream of lukewarm water. Any
particles on the surface can be swabbed gently with a series
of cotton balls, each used just one time. Dry the mirror in a
stream of air (a “blower bulb” works great), or remove any stray
drops of water with the corner of a paper towel. Dry the exterior
of the mirror cell with the towel. Cover the mirror surface with
tissue, and leave it in a warm area until completely dry before
reassembling the telescope.
When reassembling the primary mirror cell, be sure the index
groove on the inner cell’s face is oriented with the notches in
the end ring as shown in Figure 12. This assures the low point
of the primary mirror is properly oriented relative to the focuser
when the cell is reinstalled in the tube. Once reassembled, the
telescope’s mirrors will need to be re-collimated.
If the primary mirror center mark washes off during cleaning, it
is easy to re-mark the mirror’s center using a template. Trace the
outline of the primary mirror on a sheet of paper and cut out the
circle. Fold the circle precisely in half, then in half again. Cut the
very tip of the quarter circle and unfold the template. Center the
template on the primary mirror’s surface, and mark the mirror’s
center with the very tip of a felt tip marker (Figure 13).
7
Page 8
Groove
Figure 12. When reassembling the mirror cell after cleaning the
primary mirror, orient the groove on the inner cell with the notches in
the cell's end ring as shown.
Figure 13. If the center mark washes off when cleaning, use a
template to remark the primary mirror's center with a felt tip marker.
Specifications
Primary mirror material: Pyrex
Primary mirror diameter: 3.6" (91.4mm)
Primary mirror coating: Enhanced aluminum (96% reflectivity),
overcoated
Focal Length: 1240mm
®
One-Year Limited Warranty
This Orion 3.6" Clear-Aperture reflector is warranted against defects in materials or workmanship 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.
Focal Ratio: f/13.6
Secondary mirror: 28.0mm minor axis
Focuser: Rack and pinion, accepts 1.25" eyepieces, metal
focus knobs
Weight: 11.4 lbs.
Orion Telescopes & Binoculars
Post Office Box 1815, Santa Cruz, CA 95061
Customer Support Help Line (800) 676-1343 • Day or Evening
8
Loading...