Orion Shorttube 4.5"" EQ 9083 Instruction Manual

INSTRUCTION MANUAL

Orion®

ShortTube

#9083 Equatorial Reflecting Telescope

™

4.5" EQ

Providing Exceptional Consumer Optical Products Since 1975

Customer Support [phone]
E-mail: [e-mail]

Corporate Offices [phone]

P.O. Box 1815, Santa Cruz, CA 95061

IN 067 Rev. B 1298

Declination slow-motion
control cable

Finder scope

Finder scope bracket

Alignment screws (3)

Focuser

Eyepiece

Tube rings

Declination locking bolt

Declination setting circle

Counterweight shaft

Counterweight

Retaining washer and knob

Latitude lock T-bolt (not shown)

Azimuth lock knob

Accessory tray bracket

Accessory tray

Tube ring lock clamps

Collimation

thumbscrews (3)

Right ascension setting circle

Right ascension

slow motion control cable

Latitude adjustment T-bolt

Leg lock bolt

Tripod leg

Figure 1. ShortTube 4.5" EQ Parts Diagram

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Congratulations on purchasing your new ShortTube™ 4.5" EQ reflector telescope! It is a terrific starter

instrument for exploring some of the many exotic wonders our universe has to offer. Designed to be
compact and easy to use, this telescope will provide many hours of enjoyment for the whole family. It is
your ticket to a journey of discovery in the fascinating hobby of amateur astronomy.

With the ShortTube 4.5" EQ you’ll marvel at the stunning variety of mountains, craters, and valleys on
the surface of our nearest celestial neighbor, the Moon. Looking farther out into the solar system, you’ll
be awed by Saturn’s rings and by the perpetual dance of Jupiter’s brightest moons. And gazing still far­ther into space, you’ll be able to locate hundreds of mind-boggling “deep-sky” objects—sparkling star
clusters, glowing nebulas, and incredibly distant galaxies—that will dazzle and amaze you.

If you have never used a telescope before, we would like to welcome you to amateur astronomy. Take
some time to familiarize yourself with the night sky. Learn to recognize the patterns of stars in the major
constellations; a star wheel, or planisphere, available from nature stores or astronomical suppliers, will
greatly help. With a little practice, a little patience, and a reasonably dark sky away from city lights, you’ll
find your telescope to be a never-ending source of wonder, exploration, and relaxation.

Table of Contents

1. Parts List ............................................................................................................................. 3

2. Assembly ............................................................................................................................ 4

3. Balancing the Telescope .................................................................................................... 4

4. Aligning the Finder Scope .................................................................................................. 5

5. Setting Up and Using the Equatorial Mount ...................................................................... 5

6. Collimating the Optics (Aligning the Mirrors) ...................................................................... 7

7. Using Your Telescope—Astronomical Observing ............................................................... 7

8. Care and Maintenance ...................................................................................................... 10

9. Specifications ..................................................................................................................... 10

1. Parts List

Qty. Description

1 Optical tube assembly

2 Tube mounting rings

1 Equatorial mount with setting circles

2 Slow-motion control cables

1 Counterweight shaft

1 Counterweight

3 Adjustable wood tripod legs

3 Tripod leg attachment bolts (w/washers and wing nuts
attached)

3 Tripod leg lock bolts

1 Accessory tray

3 Accessory tray screws (w/washers and wing nuts attached)

1 25mm (40x) Kellner eyepiece (1.25" barrel diameter)

1 10mm (100x) Kellner eyepiece (1.25" barrel diameter)

1 5x24 crosshair finder scope

1 Finder scope bracket

1 Allen wrench

1 Tube dust cap

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.

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and automobile headlights. The glare from these lights will
greatly impair your dark-adapted night vision. Set up on a grass
or dirt surface, not asphalt, because asphalt radiates more heat.
Heat disturbs the surrounding air and degrades the images seen
through the telescope. Avoid viewing over rooftops and chim­neys, as they often have warm air currents rising from them.
Similarly, avoid observing from indoors through an open (or
closed) window, because the temperature difference between
the indoor and outdoor air will cause image blurring and distor­tion.

If at all possible, escape the light-polluted city sky and head
for darker country skies. You’ll be amazed at how many more
stars and deep-sky objects are visible in a dark sky!

Cooling the Telescope

All optical instruments need time to reach “thermal equilibri­um.” The bigger the instrument and the larger the temperature
change, the more time is needed. Allow at least a half-hour
for your telescope to cool to the temperature outdoors. In very
cold climates (below freezing), it is essential to store the tele­scope as cold as possible. If it has to adjust to more than a
40° temperature change, allow at least one hour.

Aiming the Telescope

To view an object in the main telescope, first loosen both the
R.A. and Dec. lock bolts. Aim the telescope at the object you
wish to observe by “eyeballing” along the length of the tele­scope tube (or use the setting circles to “dial in” the object’s
coordinates). Then look through the (aligned) finder scope and
move the telescope tube until the object is centered on the
crosshairs. Retighten the R.A. and Dec. lock bolts. Then center
the object on the finder’s crosshairs using the R.A. and Dec.
slow-motion controls. The object should now be visible in the
main telescope with a low-power (long focal length) eyepiece.

Focusing the Telescope

Practice focusing the telescope in the daytime before using it
for the first time at night. Start by positioning the focuser near
the center of its adjustment range. Insert an eyepiece into the
focuser and secure with the thumbscrew. Point the telescope
at a distant subject and center it in the field of view. Now,
slowly rotate one of the focusing knobs until the object comes
into sharp focus. 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 hit the exact focus point. The
telescope can only focus on objects at least 50 to 100 feet
away.

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 field of view. You can try this by
looking through the eyepiece first with your glasses on and
then with them off, and see if the glasses restrict the view to
only a portion of the full field. If they do, you can easily
observe with your glasses off by just refocusing the telescope
the needed amount.

Calculating the Magnification

It is desirable to have a range of eyepieces of different focal
lengths, to allow viewing over a range of magnifications. To calcu­late the magnification, or power, of a telescope, simply divide the
focal length of the telescope by the focal length of the eyepiece:

Telescope focal length ÷ Eyepiece focal length =

Magnification

For example, the ShortTube 4.5" EQ, which has a focal length
of 1000mm, used in combination with a 25mm eyepiece,
yields a power of

1000 ÷ 25 = 40x.

Every telescope has a useful limit of power of about 45x–60x
per inch of aperture. Claims of higher power by some tele­scope manufacturers are a misleading 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 steadiness of the air (the “seeing”)
will limit how much magnification an image can tolerate.

Always start viewing with your lowest-power (longest-focal­length) eyepiece in the telescope. After you have located and
looked at the object with it, you can try switching to a higher­power eyepiece to ferret out more detail, if atmospheric
conditions permit. If the image you see is not crisp and
steady, reduce the magnification by switching to a longer­focal-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.

Let Your Eyes Dark-Adapt

Don’t expect to go from a lighted house into the darkness of
the outdoors at night and immediately see faint nebulas, gal­axies, and star clusters—or even very many stars, for that
matter. Your eyes take about 30 minutes to reach perhaps
80% of their full dark-adapted sensitivity. As your eyes
become dark-adapted, more stars will glimmer into view and
you’ll be able to see fainter details in objects you view in your
telescope. Exposing your eyes to very bright daylight for
extended periods of time can adversely affect your night
vision for days. So give yourself at a little while to get used to
the dark before you begin observing.

To see what you’re doing in the darkness, use a red-filtered flash­light rather than a white light. Red light does not spoil your eyes’
dark adaptation like white light does. A flashlight with a red LED
light, like the RedBeam LED Flashlight (Orion #5744), is ideal ,
or you can cover the front of a regular incandescent flashlight with
red cellophane or paper. Beware, too, that nearby porch lights,
streetlights and car headlights will ruin your night vision.

“Seeing” and Transparency

Atmospheric conditions vary significantly from night to night.
“Seeing” refers to the steadiness of the Earth’s atmosphere at
a given time. In conditions of poor seeing, atmospheric turbu­lence causes objects viewed through the telescope to “boil.”
If, when you look up at the sky with just your eyes, the stars
are twinkling noticeably, the seeing is bad and you will be
limited to viewing with low powers (bad seeing affects images

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rotate the mount so the telescope points North. Retighten
the azimuth lock knob.

The equatorial mount is now polar-aligned for casual observ­ing. Note that from this point on in your observing session,
you should not make any further adjustments in the azimuth
or the latitude of the mount, nor should you move the tripod.
Doing so will nullify the polar alignment. The telescope should
be moved only about its R.A. and Dec. axes.

Tracking Celestial Objects

When you observe a celestial object through the telescope,
you’ll see it drift slowly across the field of view. To keep it in
the field, if your equatorial mount is polar aligned, just turn the
R.A. slow-motion control. The Dec. slow-motion control is not
needed for tracking. Objects will appear to move faster at
higher magnifications, because the field of view is narrower.

Understanding the Setting Circles

The setting circles on an equatorial mount enable you to
locate celestial objects by their “coordinates.” Every object
resides in a specific location on the “celestial sphere.” That
location is denoted by two numbers: its right ascension (R.A.)
and declination (Dec.). In the same way, every location on
Earth can be described by its longitude and latitude. R.A. is
similar to longitude on Earth, and Dec. is similar to latitude.
The R.A. and Dec. values for celestial objects can be found in
any star atlas or star catalog.

The R.A. setting circle is scaled in hours, from 1 through 24,
with small hash marks in between representing 10-minute
increments (there are 60 minutes in 1 hour of R.A.). The num­bers closest to the R.A. gear apply to viewing in the Southern
Hemisphere, while the numbers above them apply to viewing
in the Northern Hemisphere. The Dec. setting circle is scaled
in degrees, with each small hash mark representing 2.5
degrees (there are 60 arc-minutes in 1 degree of declination).

So, the coordinates for the Orion Nebula listed in a star atlas
will look like this:

R.A. 5h 35.4m Dec. –5° 27'

That’s 5 hours and 35.4 minutes in right ascension, and –5
degrees and 27 arc-minutes in declination (the negative sign
denotes south of the celestial equator).

Before you can use the setting circles to locate objects, the
mount must be well polar aligned, and the R.A. setting circle
must be calibrated (the Dec. setting circle is already perma­nently calibrated at the factory).

Calibrating the Right Ascension Setting Circle

1. Identify a bright star near the celestial equator and look up
its coordinates in a star atlas.

2. Loosen the R.A. and Dec. lock bolts on the equatorial
mount, so the telescope optical tube can move freely.

3. Point the telescope at the bright star near the celestial
equator whose coordinates you know. This information can
be taken from any star chart. Center the star in the tele­scope’s field of view. Retighten the R.A. and Dec. lock bolts.

4. Rotate the R.A. setting circle so the pointer indicates the
R.A. listed for that object in the star atlas.

Finding Objects With the Setting Circles

Now that both setting circles are calibrated, look up in a star
atlas the coordinates of an object you wish to view.

1. Loosen the Dec. lock bolt and rotate the telescope until
the Dec. value from the star atlas matches the reading on
the Dec. setting circle. Retighten the lock bolt.

2. Loosen the R.A. lock bolt and rotate the telescope until the
R.A. value from the star atlas matches the reading on the
R.A. setting circle. Retighten the lock bolt.

Most setting circles are not accurate enough to put an object
dead-center in your finder scope’s field of view, but they’ll get
you close, assuming the equatorial mount is accurately polar­aligned. The R.A. setting circle must be recalibrated every time
you wish to locate a new object. Do so by calibrating the setting
circle for the centered object before moving on to the next one.

Confused About Pointing the Telescope?

Beginners occasionally experience some confusion about
how to point the telescope overhead or in other directions. In
Figure 1 the telescope is pointed north, as it would be during
polar-alignment. The counterweight shaft is oriented down­ward. But it will not look like that when the telescope is pointed
in other directions. Let’s say you want to view an object that is
directly overhead, at the zenith. How do you do it?

One thing you DO NOT do is make any adjustment to the
latitude adjustment knob. That will nullify the mount’s polar
alignment. Remember, once the mount is polar-aligned, the
telescope should be moved only on the R.A. and Dec. axes.
To point the scope overhead, first loosen the R.A. lock bolt
and rotate the telescope on the R.A. axis until the counter­weight shaft is horizontal (parallel to the ground). Then loosen
the Dec. lock bolt and rotate the telescope until it is pointing
straight overhead. The counterweight shaft is still horizontal.
Then retighten both lock bolts.

Similarly, to point the telescope directly south, the counter­weight shaft should again be horizontal. Then you simply rotate
the scope on the Dec. axis until it points in the south direction.

What if you need to aim the telescope directly north, but at an
object that is nearer to the horizon than Polaris? You can’t do
it with the counterweight down as pictured in Figure 1. Again,
you have to rotate the scope in R.A. so the counterweight
shaft is positioned horizontally. Then rotate the scope in Dec.
so it points to where you want it near the horizon.

To point the telescope to the east or west, or in other directions,
you rotate the telescope on its R.A. and Dec. axes. Depending on
the altitude of the object you want to observe, the counterweight
shaft will be oriented somewhere between vertical and horizontal.

The key things to remember when pointing the telescope is that
a) you only move it in R.A. and Dec., not in azimuth or latitude
(altitude), and b) the counterweight and shaft will not always
appear as it does in Figure 1. In fact, it almost never will!

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2. Assembly

Carefully open all of the boxes in the shipping container.
Make sure all the parts listed in section 2 are present. Save
the boxes and packaging material. In the unlikely event that
you need to return the telescope, you must use the original
packaging.

Assembling the telescope for the first time should take about
20 minutes. All bolts should be tightened securely to eliminate
flexing and wobbling, but only tighten them “finger tight.” Be
careful not to over-tighten so as not to strip the threads. Refer
to Figure 1 during the assembly process.

During assembly (and anytime, for that matter), DO NOT
touch the surfaces of the telescope mirrors or the lenses of
the finder scopes or eyepieces with your fingers. The optical
surfaces have delicate coatings on them that can easily be
damaged if touched inappropriately. NEVER remove any lens
assembly from its housing for any reason, or the product war­ranty and return policy will be voided.

1. Lay the equatorial mount on its side. Attach the tripod
legs, one at a time, to the base of the mount by sliding a
tripod leg attachment bolt through the top of a leg and
through the hole in the base of the mount. The washers
should be on the outside of the tripod legs. Secure the
wing nuts barely finger-tight. Note that the hinged acces­sory tray bracket on each leg should face inward.

2. Attach and tighten the leg lock bolts at the base of the
legs. For now, keep the legs at their shortest (fully retract­ed) length; you can extend them to a more desirable
length later, after the scope is completely assembled.

3. With the tripod legs now attached to the equatorial mount,
stand the tripod upright (be careful!) and spread the legs
apart enough to attach the accessory tray to the three
hinged tray brackets on the legs. The brackets should be
positioned underneath the tray. Use the three small acces­sory tray screws and wing nuts provided. Do not tighten
the wing nuts yet.

4. Now, with the accessory tray attached loosely, spread the
tripod legs apart as far as they will go, until the accessory
tray brackets are taut. Then tighten the wing nuts.

5. Next, tighten the wing nuts on the tripod leg attachment
bolts at the base of the equatorial mount, so that the legs
are securely fastened.

6. Orient the equatorial mount as it appears in Figure 1, at a
latitude of about 40°, i.e., so that the pointer next to the
latitude scale is pointing to the hash mark at “40.” To do
this, loosen the latitude lock t-bolt (central to the latitude
scale), and turn the latitude adjustment t-bolt until the
pointer and the “40” line up. Then retighten the latitude
lock t-bolt. Also tighten the declination (Dec.) and right
ascension (R.A.) lock bolts.

7. Slide the counterweight onto the counterweight shaft, and
secure it on the shaft with the bolt on the counterweight.
The washer and bolt on the end of the counterweight shaft
will prevent the counterweights from slipping off the shaft

and possibly onto your foot if the counterweight lock bolt
should come loose!

8. Grip the counterweight with one hand and thread the shaft
into the equatorial mount (at the base of declination axis)
with the other hand. When it is threaded in as far as it will
go, position the counterweight about halfway up the shaft
and retighten the counterweight lock bolt.

9. Attach the two tube rings to the equatorial head, using the
tube ring bolts attached to the tube rings. Open the tube rings.

10. Lay the telescope optical tube in the felt-lined tube rings at
about the midpoint of the tube’s length. Rotate the tube in
the rings so the focuser is angled somewhere between
horizontal and straight up. Close the rings over the tube
and tighten the knurled ring clamps finger-tight to secure
the telescope in position.

11. Now attach the two slow-motion cables to the R.A. and
Dec. worm gear shafts of the equatorial mount by posi­tioning the setscrew on the end of the cable over the
indented slot on the worm gear shaft, then tightening the
setscrew. On the R.A. worm gear shaft, a cable can be
attached to either end of the shaft, whichever is most con­venient for you.

12. To install the finder scope bracket on the optical tube
(adjacent to the focuser), first remove the round nuts on
the two mounting screws. Do not loosen the small hex
nuts on the mounting screws. Place the finder scope
bracket over the two screws. Orient the bracket so that it
angles back towards the rear of the telescope. Replace
the round nuts and tighten finger-tight.

13. Place the finder scope in the finder bracket by first backing
off all three alignment screws until the screw tips are flush
with the inside diameter of the finder bracket. Slide the finder
scope through the finder bracket ring with the larger (objec­tive) end of the finder scope pointing in the same direction as
the open end of the main telescope. Tighten the three align­ment screws equally to secure the finder scope in place.

14. Remove the cap on the focuser drawtube and insert the
25mm Kellner eyepiece. You will need to remove the entire
cap, which requires unthreading the thumbscrew on the
end of the focuser drawtube. Secure the eyepiece in place
with the thumbscrew.

15. Remove the entire tube dust cover from the front of the
telescope.

3. Balancing the Telescope

To insure smooth movement of the telescope on both axes of
the equatorial mount, it is imperative that the optical tube be
properly balanced. We will first balance the telescope with
respect to the R.A. axis, then the Dec. axis.

1. Keeping one hand on the telescope optical tube, loosen
the R.A. lock bolt. Make sure the Dec. lock bolt is locked,
for now. The telescope should now be able to rotate freely
about the R.A. axis. Rotate it until the counterweight shaft
is parallel to the ground (i.e., horizontal).

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2. Now loosen the counterweight lock bolt and slide the weight
along the shaft until it exactly counterbalances the tele­scope. That’s the point at which the shaft remains horizontal
even when you let go of the telescope with both hands.

3. Retighten the counterweight lock bolt. The telescope is
now balanced on the R.A. axis.

4. To balance the telescope on the Dec. axis, first tighten the
R.A. lock bolt, with the counterweight shaft still in the
horizontal position.

5. With one hand on the telescope optical tube, loosen the
Dec. lock bolt. The telescope should now be able to rotate
freely about the Dec. axis. Loosen the knurled tube ring
clamps a few turns, until you can slide the telescope tube
forward and back inside the rings (this can be aided by
using a slight twisting motion on the optical tube while you
push or pull on it).

6. Position the telescope so that it remains horizontal when
you carefully let go with both hands. This is the balance
point. Before clamping the rings tight again, rotate the
telescope so the eyepiece is at a convenient angle for view­ing. When you are actually observing with the
telescope, you can adjust the eyepiece position by
loosening the tube ring clamps and rotating the optical tube.

7. Retighten the knurled tube ring lock clamps.

The telescope is now balanced on both axes. Now when you
loosen the lock bolt on one or both axes and manually point
the telescope, it should move without resistance and should
not drift from where you point it.

4. Aligning the Finder Scope

A finder scope has a wide field of view to facilitate the location
of objects for subsequent viewing through the main tele­scope, which has a much narrower field of view. The finder
scope and the main telescope must be aligned so they point
to exactly the same spot in the sky.

Alignment is easiest to do in daylight hours. First, insert the
lowest-power (25mm) eyepiece into the main telescope’s
focuser. Then loosen the R.A. and Dec. lock bolts so the
telescope can be moved freely.

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. Move the telescope so the target object appears in the
very center of the field of view when you look into the eye­piece. Now tighten the R.A. and Dec. lock bolts. Use the
slow-motion control knobs to recenter the object in the field of
view, if it moved off-center when you tightened the lock bolts.

Now look through the finder scope. Is the object centered in
the finder scope’s field of view, i.e., on the crosshairs? If not,
hopefully it will be visible somewhere in the field of view, so
that only fine adjustment of the alignment screws will be
needed. Otherwise you’ll have to make coarser adjustments to
the alignment screws to redirect the aim of the finder scope.

Use the three alignment screws to center the object on the
crosshairs of the finder scope. Then look again into the main

telescope’s eyepiece and see if it is still centered there as well.
If it isn’t, repeat the entire process, making sure not to move the
main telescope while adjusting the alignment of the finder scope.

Note that the image seen through the finder scope appears
upside-down. This is normal for astronomical finder scopes.

5. Setting Up and Using the
Equatorial Mount

When you look at the night sky, you no doubt have noticed the
stars appear to move slowly from east to west over time. That
apparent motion is caused by the Earth’s rotation (from west to
east). An equatorial mount (Figure 2) is designed to compensate
for that motion, allowing you to easily “track” the movement of
astronomical objects, thereby keeping them from drifting out of
the telescope’s field of view while you’re observing.

This is accomplished by slowly rotating the telescope on its right
ascension (polar) axis, using only the R.A. slow-motion cable. But
first the R.A. axis of the mount must be aligned with the Earth’s
rotational (polar) axis — a process called polar alignment.

Polar Alignment

For Northern Hemisphere observers, approximate polar
alignment is achieved by pointing the mount’s R.A. axis at the
North Star, which is also called Polaris. It lies within 1° of the
north celestial pole (NCP), which is an extension of the
Earth’s rotational axis out into space. Stars in the Northern
Hemisphere appear to revolve around Polaris.

To find Polaris in the sky, look north and locate the pattern of
the Big Dipper (Figure 3). The two stars at the end of the
“bowl” of the Big Dipper point right to Polaris.

Observers in the Southern Hemisphere aren’t so fortunate to
have a bright star so near the south celestial pole (SCP). The
star Sigma Octantis lies about 1° from the SCP, but it is
barely visible with the naked eye (magnitude 5.5).

For general visual observation, an approximate polar align­ment is sufficient.

1. Level the equatorial mount by adjusting the length of the
three tripod legs.

2. Loosen the latitude lock t-bolt. Turn the latitude adjustment
t-bolt and tilt the mount until the pointer on the latitude
scale is set at the latitude of your observing site. If you
don’t know your latitude, consult a geographical atlas to
find it. For example, if your latitude is 35° North, set the
pointer to +35. Then retighten the latitude lock t-bolt. The
latitude setting should not have to be adjusted again
unless you move to a different viewing location some dis­tance away.

3. Loosen the Dec. lock bolt and rotate the telescope optical tube
until it is parallel with the R.A. axis. The pointer on the Dec.
setting circle should read 90°. Retighten the Dec. lock bolt.

4. Loosen the azimuth lock knob and rotate the mount in
azimuth (left-to-right) so the telescope tube (and R.A.
axis) points roughly at Polaris. If you cannot see Polaris
directly from your observing site, consult a compass and

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6. Collimating the Optics
(Aligning the Mirrors)

Collimation is the process of adjusting the mirrors so they are
perfectly aligned with each other. Your telescope’s optics were
aligned at the factory, and should not need much adjustment
unless the telescope was roughly handled during shipment.
Accurate alignment is important to insuring the peak perfor­mance of your telescope, so it should be checked occasionally.
Collimation is easy to do and should be done in daylight.

To check the collimation, remove the eyepiece and look down
the focuser drawtube. You should see the secondary mirror
centered in the drawtube, the reflection of the primary mirror
centered in the secondary mirror, and the reflection of the
secondary mirror (and your eye) centered in the reflection of
the primary mirror, as in Figure 4D. If anything is off-center,
follow the collimation procedure below.

It helps to put a piece of white paper on the inside of the opti­cal tube opposite the focuser. The white paper forms a bright
background behind the secondary mirror, making it easier to
distinguish the mirror holder from the background.

Use a Collimation Tool

To aid in centering your line of sight down the focuser draw­tube, and in centering the mirror reflections during collimation,
it is very helpful to use a precision collimating tool containing
crosshairs, such as the Orion Collimating Eyepiece (Orion
#3640). We highly recommend you purchase one.

Aligning the Secondary Mirror

With eyepiece removed, look straight down the open focuser
drawtube at the secondary (diagonal) mirror. Ignore the reflections
for the time being. The secondary mirror should be centered in the
field of view. If it isn’t, it must be adjusted. (It helps to adjust the
secondary mirror in a brightly lit room with the telescope pointed
toward a bright surface, such as white paper or a wall.)

If the secondary mirror is not centered in the focuser draw­tube (in the direction parallel to the length of the telescope),
loosen the three small alignment screws in the center hub of
the secondary mirror holder several turns with the provided
Allen wrench. Now hold the secondary mirror stationary (be
careful not to touch the surface of the secondary mirror!),
while turning the central Phillips-headed bolt. Turning the bolt
clockwise will move the secondary mirror towards the front
opening of the optical tube, while turning the bolt counter­clockwise will move the secondary mirror towards the primary
mirror. When the secondary mirror is centered in the focuser
drawtube (as in Figure 4B), rotate the secondary mirror holder
slightly side-to-side until the reflection of the primary mirror is
as centered in the secondary mirror as it will get. It still may not
be perfectly centered yet, but that is OK. Now tighten the three
small alignment screws to secure the secondary mirror in that
position. This adjustment will rarely need to be done, if ever.

If the entire primary mirror reflection is not visible in the sec­ondary mirror (as it is not in Figure 4B), adjust the tilt of the
secondary mirror by alternately loosening one of the three
alignment screws of the secondary mirror holder a turn or two

and tightening another one. Use the provided Allen wrench to
do this. The goal is to center the primary mirror reflection in
the secondary mirror, as depicted in Figure 4C. Don’t worry
that the reflection of the secondary mirror (the smallest circle,
with your eye reflected in it) is off-center (as also is the case
in Figure 4C); you will fix that in the next step.

Adjusting the Primary Mirror

The final adjustment is made to the primary mirror. It will need
adjustment if, as in Figure 4C, the secondary mirror is cen­tered under the focuser and the reflection of the primary mirror
is centered in the secondary mirror, but the small reflection of
the secondary mirror (with your eye inside) is off-center.

The tilt of the primary is adjusted with the three knurled
thumbscrews on the back end of the optical tube (bottom of
the mirror cell). The Phillips-head screws next to each of the
three knurled thumbscrews serve to lock the mirror in place
once the tilt has been adjusted. Start by loosening each of
these Phillips-head screws a few turns. Now, adjust the tilt of
the mirror by turning one of the knurled 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. If not, try turning the
knurled thumbscrew in the opposite direction. Repeat this
process on the other two collimation screws, if necessary. It
will take a little trial and error to get a feel for how to tilt the
mirror in this way to center the reflection. (It helps to have two
people for primary mirror collimation, one to look in the
focuser while the other adjusts the collimation thumbscrews.)
When the reflection of the secondary mirror (and your eye)
are centered, retighten the three Phillips-head screws.

The view through the Collimating Eyepiece should now
resemble Figure 4D. The secondary mirror is centered in the
focuser; the reflection of the primary mirror is centered in the
secondary mirror, and the reflection of the secondary mirror
is centered in the reflection of the primary mirror.

A simple star test will tell you whether the optics are accu­rately collimated.

Star-Testing Your Telescope

When it is dark, point the telescope at a bright star and accu­rately center it in the eyepiece’s field-of-view with the R.A. and
Dec. slow-motion controls. Slowly rack the image out of focus
with the focusing knob. If the telescope is correctly collimated,
the expanding disk should be a perfect circle. If it is unsym­metrical, the scope is out of collimation. 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 doughnut. If the
“hole” appears off-center, the telescope is out of collimation.

7. Using Your Telescope—

Astronomical Observing

Choosing an Observing Site

When selecting a location for observing, get as far away as pos­sible from direct artificial light such as streetlights, porch lights,

8

ing skills get sharper, you will be able to discern more subtle
details.

Remember that the higher the magnification you use, the dim­mer the image will appear. So stick with low power when
observing deep-sky objects, because they’re already very faint.

Consult a star atlas or observing guide for information on find­ing and identifying deep-sky objects. Some good sources to
start with are the Orion DeepMap 600 (Orion #4150),
Edmund Mag 6 Star Atlas (Orion #6142), Turn Left at Orion
(Orion #51315), and The Universe From Your Backyard
(Orion #51530).

8. 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
cap on the front of the telescope when it is not in use.

Your ShortTube 4.5" EQ 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 a household
cleaner such as Windex or Formula 409.

Cleaning Lenses

Any quality optical lens cleaning tissue and optical lens clean­ing fluid specifically designed for multi-coated optics can be
used to clean the exposed lenses of your eyepieces or finder
scope. Never use regular glass cleaner or cleaning fluid
designed for eyeglasses. 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 in a
circular motion, 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. On larger lenses, clean only a small area at a time, using
a fresh lens tissue on each area. Never reuse tissues.

Cleaning Mirrors

You should not have to clean your telescope’s mirrors very
often; normally once every year or so. Covering your tele­scope 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 visual performance of the telescope.

The large primary mirror and the elliptical secondary mirror of
your telescope are front-surface aluminized and over-coated
with hard silicon monoxide, which prevents the aluminum from
oxidizing. These coatings normally last through many, many
years of use before requiring recoating (which is easily done).

To clean the secondary mirror, remove it from the secondary
mirror holder. Do this by holding the secondary mirror station­ary while turning the central, Phillips head bolt on the
secondary mirror holder counterclockwise. Handle it carefully
by the edges only; do not touch the mirror surface. Then follow
the same procedure described below for cleaning the primary
mirror.

To clean the primary mirror, carefully remove the mirror cell
from the telescope. This is done by removing the three small
Phillips head screws on the outer edge of the mirror cell.
Remove the mirror from the cell by loosening the two Phillips
head screws on each of the three mirror clips. Be careful not
to touch the front surface of the mirror with your fingers! Set
the mirror 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 rub­bing alcohol. Submerge the mirror (aluminized face up) in the
water and let it soak for several minutes (or hours if it’s a very
dirty mirror). Wipe the mirror under water with clean cotton
balls, using extremely light pressure and stroking in straight
lines across the surface. 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 clean 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. Water will run off a clean surface. Dry the cell and
exposed surfaces with a towel (not the mirror surface!). Cover
the mirror surface with Kleenex, and leave the entire assem­bly in a warm area until it is completely dry before reassembling
the telescope.

9. Specifications

Optical tube: Aluminum

Primary mirror diameter: 4.5" (114mm)

Focal length: 1000mm

Focal ratio: f/8.8

Eyepieces: 25mm and 10mm Kellners, fully coated, 1.25"

Magnification: 40x (with 25mm), 100x (with 10mm)

Focuser: Rack and pinion

Finder scope: 5x magnification, 24mm aperture, crosshairs

Mount: German-type equatorial

Tripod: Hardwood

9

at high powers more severely). Planetary observing may also
be poor.

In conditions of good seeing, star twinkling is minimal and
images appear steady in the eyepiece. Seeing is best over­head, worst at the horizon. Also, seeing generally gets better
after midnight, when much of the heat absorbed by the Earth
during the day has radiated off into space.

Avoid looking over buildings, pavement, or any other source
of heat, as they will cause “heat wave” disturbances that will
distort the image you see through the telescope.

Especially important for observing faint objects is good “trans­parency”—air free of moisture, smoke, and dust. All tend to
scatter light, which reduces an object’s brightness. Transparency
is judged by the magnitude of the faintest stars you can see with
the unaided eye (6th magnitude or fainter is desirable).

How to Find Interesting Celestial Objects

To locate celestial objects with your telescope, you first 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, unless, of course,
you look up its celestial coordinates and use the telescope’s set­ting circles. Even then, it would be good to know in advance
whether that constellation will be above the horizon at the time
you plan to observe. A simple planisphere, or star wheel, can be
a valuable tool both for learning the constellations and for deter­mining which ones are visible on a given night at a given time.

A good star chart or atlas will come in very handy for helping
find objects among the dizzying multitude of stars overhead.
Except for the Moon and the brighter planets, it’s pretty time­consuming and frustrating to hunt for objects randomly,
without knowing where to look. You should have specific tar­gets in mind before you begin observing.

Start with a basic star atlas, one that shows stars no fainter
than 5th or 6th magnitude. In addition to stars, the atlas will
show the positions of a number of interesting deep-sky
objects, with different symbols representing the different
types of objects, such as galaxies, open star clusters, globu­lar clusters, diffuse nebulas, and planetary nebulas. So, for
example, your atlas might show that there is a globular cluster
sitting just above the lid of the “Teapot” pattern of stars in
Sagittarius. You then know to point your telescope in that
direction to home in on the cluster, which happens to be

6.9-magnitude Messier 28 (M28).

You can see a great number and variety of astronomical
objects with your ShortTube 4.5" EQ, including:

The Moon

With its rocky, cratered surface, the Moon is one of the easi­est and most interesting targets to view with your telescope.
The best time to observe our one and only natural satellite is
during a partial phase, that is, when the Moon is NOT full.
During partial phases, shadows on the surface reveal more
detail, especially right along the border between the dark and
light portions of the disk (called the “terminator”). A full Moon
is too bright and devoid of surface shadows to yield a pleas­ing view. Use a Moon Filter (Orion #5662) to dim the Moon

when it is very bright. It simply threads onto the bottom of the
eyepieces (you must first remove the eyepiece from the
focuser to attach the Moon filter).

The Planets

The planets don’t stay put like the stars (they don’t have fixed R.A.
and Dec. coordinates), so you’ll have to refer to charts published
monthly in Astronomy, Sky & Telescope, or other astronomy
magazines to locate them. Venus, Mars, Jupiter, and Saturn are
the brightest objects in the sky after the Sun and the Moon. Not
all four of these planets are normally visible at any one time.

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 see­ing) 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.

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.

Stars

Stars will appear like twinkling points of light in the telescope. Even
powerful telescopes cannot magnify stars to appear as 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 constellation 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.

Deep-Sky Objects

Under dark skies, you can observe a wealth of fascinating
deep-sky objects, including gaseous nebulas, open and
globular star clusters, and different types of galaxies. Most
deep-sky objects are very faint, so it is important that you find
an observing site well away from light pollution. Take plenty of
time to let your eyes adjust to the darkness. Don’t expect
these subjects to appear like the photographs you see in
books and magazines; most will look like dim gray smudges.
(Our eyes are not sensitive enough to see color in such faint
objects.) But as you become more experienced and your observ-

10

Declination lock

bolt

Latitude scale

Latitude
adjustment T-bolt

RIGHT ASCENSION

(POLAR) AXIS

Figure 2

DECLINATION AXIS

Right ascension

lock bolt

Counterweight

lock knob

Latitude lock

T-bolt

Little Dipper

(in Ursa Minor)

Big Dipper

(in Ursa Major)

Pointer Stars

N.C.P.

Polaris

Cassiopeia

To find Polaris in the night sky, look north and find the Big Dipper. Extend an imaginary line from the two “Pointer Stars” in
the bowl of the Big Dipper. Go about 5 times the distance between those stars and you’ll reach Polaris, which lies within 1°
of the north celestial pole (NCP).

Figure 3

11

Figure 4B. Secondary mirror
centered under focuser
tube, viewed through
the Collimating Eyepiece
(as are the next two
illustrations).

Figure 4A. The view down the focuser tube of a Newtonian
reflector with eyepiece removed. In this example, the optical
system is badly out of collimation.

One-Year Limited Warranty

This Orion ShortTube 4.5" EQ 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; [phone].

Figure 4C. Secondary
mirror correctly aligned
(tilted).

Figure 4D. Primary mirror
correctly aligned. The
telescope’s optical system
is now collimated.

Orion Telescopes & Binoculars

Post Office Box 1815, Santa Cruz, CA 95061

Customer Support Help Line [phone] • Day or Evening