ORION TELESCOPES & BINOCULARS ShortTube 4.5 EQ 9849 User manual

IN 187 Rev. A 05/02
Providing Exceptional Consumer Optical Products Since 1975
Customer Support [phone]
E-mail: [email protected]
Corporate Offices [phone]
P.O. Box 1815, Santa Cruz, CA 95061
INSTRUCTION MANUAL
Orion®
ShortTube™ 4.5" EQ
#9849 Equatorial Reflecting Telescope

2
Figure 1. The ShortTube 4.5 EQ.
EZ Finder II
Focuser
Eyepiece
Tube rings
EZ Finder II bracket
Bracket securing thumbnuts
Right ascension setting circle
Right ascension
slow motion control cable
Latitude adjustment T-bolt
Tripod leg
Leg lock knob
Declination slow-motion
control cable
Declination lock knob
Declination setting circle
Counterweight shaft
Counterweight
Counterweight lock knob
Latitude lock T-bolt
(not shown)
Azimuth lock knob
Accessory tray bracket
Accessory tray
Tripod leg

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Table of Contents
1. Unpacking . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Parts List . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Assembly . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Getting Started . . . . . . . . . . . . . . . . . . . . 5
5. Setting Up and Using the
Equatorial Mount . . . . . . . . . . . . . . . . . . . 7
6. Collimating the Optics
(Aligning the Mirrors) . . . . . . . . . . . . . . . . 9
7. Astronomical Observing . . . . . . . . . . . . 11
8. Care and Maintenance . . . . . . . . . . . . . 14
9. Specifications . . . . . . . . . . . . . . . . . . . . 14
1. Unpacking
The entire telescope system will arrive in one box. Be careful
unpacking the box.We recommend keeping the original ship-
ping containers. In the event that the telescope needs to be
shipped to another location, or returned to Orion for warranty
repair, having the proper shipping containers will help ensure
that your telescope will survive the journey intact.
Make sure all the parts in the Parts List are present. Be sure
to check boxes carefully, as some parts are small. If anything
appears to be missing or broken, immediately call Orion
Customer Support (800-676-1343) for assistance.
2. Parts List
Qty. Description
1 Optical tube assembly
1 Optical tube dust cap
2 Tube mounting rings
1 Equatorial mount
1 EZ Finder II reflex sight with mounting bracket
2 Slow-motion control cables
3 Tripod legs with attached accessory tray bracket
3 Leg lock knobs
3 Tripod attachment screws with wing nuts and
washers
1 Counterweight shaft
1 Counterweight
1 Tripod accessory tray
1 25mm Explorer II eyepiece
1 10mm Explorer II eyepiece
1 Collimation cap
3. Assembly
Assembling the telescope for the first time should take about
30 minutes.You will need a Phillips head screwdriver in addi-
tion to the tools provided. All screws should be tightened
securely to eliminate flexing and wobbling, but be careful not
to over-tighten or the threads may strip. Refer to Figures 1
and 2 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 EZ
Finder II 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.
Congratulations on your purchase of a quality Orion telescope. Your new ShortTube 4.5 is a terrific
starter instrument for exploring the exotic wonders of the night sky. Designed to be compact and easy
to use, this telescope will provide many hours of enjoyment for the whole family.
If you have never owned 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. 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.
These instructions will help you set up, properly use and care for your telescope. Please read them
over thoroughly before getting started.
WARNING: Never look directly at the Sun
through your telescope—even for an instant—
without a professionally made solar filter that
completely covers the front of the instrument, or
permanent eye damage could result.Young
children should use this telescope only with
adult supervision.

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1. Lay the equatorial mount on its side. Attach the tripod
legs one at a time to the mount using the tripod attach-
ment screws. Line up the holes in the top of the tripod leg
with the holes in the base of the mount, and install a
screw so it passes through the leg and the mount with
one washer on both sides of the tripod leg. Tighten the
wingnuts only finger-tight, for now.
2. Install and tighten the leg lock knobs on the bottom
braces of the tripod legs. For now, keep the legs at their
shortest (fully retracted) length; you can extend them to a
more desirable length later, after the tripod is completely
assembled.
3. Stand the tripod and mount upright and spread the tripod
legs apart as far as they will go, until the accessory tray
bracket is taut. Connect the accessory tray to the acces-
sory tray bracket with the three wing screws already
installed in the tray. Do this by pushing the wing screws
up through the holes in the accessory tray bracket and
threading them into the holes in the accessory tray.
4. Next, tighten the screws at the tops of the tripod legs, so
the legs are securely fastened to the mount. Use the
Phillips head screwdriver and your fingers to do this.
5. Orient the equatorial mount as it appears in Figure 2, at a
latitude of about 40°, i.e., so the pointer next to the lati-
tude scale is pointing to the mark at “40.” To do this,
loosen the latitude lock T-bolt, and turn the latitude
adjustment T-bolt until the pointer and the “40” line up.
Then retighten the latitude lock T-bolt. The declination
(Dec.) and right ascension (R.A.) axes may need re-posi-
tioning (rotation) as well. Be sure to loosen the R.A. and
Dec. lock knobs before doing this. Retighten the R.A. and
Dec. lock knobs once the equatorial mount is properly
oriented.
6. Thread the counterweight shaft into the equatorial mount
at the base of the declination axis until tight.
7. Remove the screw and washer on the bottom of the
counterweight shaft and slide the counterweight onto the
shaft. Make sure the counterweight lock knob is ade-
quately loosened to allow the counterweight shaft to pass
through the hole. Position the counterweight about
halfway up the shaft and tighten the lock knob. Replace
the screw and washer on the end of the shaft.
8. Attach the two tube rings to the equatorial head using the
hex head screws that come installed in the rings.Remove
the screws, then push them, with the washers still
attached, up through the holes in the tube ring mounting
plate (on the top of the equatorial mount) and rethread
them into the bottom of the tube rings.Tighten the screws
securely with the included wrench. Open the tube rings
by loosening the knurled ring clamps.
9. Attach the two slow-motion cables to the R.A. and Dec.
worm gear shafts of the equatorial mount by positioning
the thumbscrew on the end of the cable over the indented
slot on the worm gear shaft and then tightening the
thumbscrew. We recommend that the shorter cable be
used on the R.A. worm gear shaft and the longer cable
on the Dec. worm gear shaft.
10.Loosen and remove the EZ Finder II bracket securing
thumbnuts from the optical tube assembly. Place the
holes in the bottom of the EZ Finder II bracket over the
two threaded shafts coming out of the optical tube.
Replace the thumbnuts to secure the bracket to the opti-
cal tube.Refer to Figure 1 for the proper orientation of the
bracket.
11.Attach the EZ Finder II to its mounting bracket by loosen-
ing the two thumbscrews on the EZ Finder II and sliding it
Figure 2. The ShortTube 4.5’s equatorial mount.
Right ascension
lock knob
Right ascension
setting circle
Latitude scale
Latitude lock T-bolt
Latitude adjustment
T-bolt
Declination lock knob
Declination
setting circle
Azimuth lock knob

5
onto the bracket. Retighten the thumbscrews to secure
the EZ Finder II in place.
12.Insert the 25mm Explorer II eyepiece into the focuser
drawtube and secure it in place with the thumbscrews.
4. Getting Started
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 knob. Make sure the Dec. lock knob is
locked, for now. The telescope should now be able to
rotate freely about the R.A. axis. Rotate it until the coun-
terweight shaft is parallel to the ground (i.e., horizontal).
2. Now loosen the counterweight lock knob and slide the
weight along the shaft until it exactly counterbalances the
telescope (Figure 3a). That’s the point at which the shaft
remains horizontal even when you let go of the telescope
with both hands (Figure 3b).
3. Retighten the counterweight lock knob. 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 knob, with the counterweight shaft still in the
horizontal position.
5. With one hand on the telescope optical tube, loosen the
Dec. lock knob. The telescope should now be able to
rotate freely about the Dec. axis. Loosen the 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) (Figure 3c).
6. Position the telescope so it remains horizontal when you
carefully let go with both hands.This is the balance point
(Figure 3d). 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 tele-
Figure 3a. Proper orientation of the equatorial mount requires
that the telescope tube be balanced on both the R.A. and Dec.
axes. With the R.A. lock knob released, slide the counterweight
along the counterweight shaft until it just counterbalances the tube.
Figure 3b. When you let go with both hands, the tube should not
drift up or down.
Figure 3c. With the Dec. lock knob released, loosen the tube
ring lock clamps a few turns and slide the telescope forward or back
in the tube rings.
Figure 3d. When the tube is balanced about the Dec. axis, it will
not move when you let go.

6
scope, you can adjust the eyepiece position by loosening
the tube rings and rotating the optical tube.
7. Retighten the knurled tube ring clamps.
The telescope is now balanced on both axes. Now when you
loosen the lock knob on one or both axes and manually point
the telescope, it should move without resistance and should
not drift from where you point it.
Focusing the Telescope
With the 25mm Explorer II eyepiece in the focuser, move the
telescope so the front (open) end is pointing in the general
direction of an object at least 1/4-mile away. Now with your
fingers, slowly rotate one of the focusing knobs until the
object comes into sharp focus. Go a little bit beyond sharp
focus until the image starts to blur again, then reverse the
rotation of the knob, just to make sure you’ve hit the exact
focus point.
Do You Wear Eyeglasses?
If you wear eyeglasses, you may be able to keep them on
while you observe. In order to do this, your eyepiece must
have enough “eye relief” to allow you to see the entire field of
view with glasses on.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 the glasses do restrict the field of view, you
may be able to observe with your glasses off by just refocus-
ing 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 field of view, you may
want to purchase additional eyepieces that have longer eye
relief.
Operating the EZ Finder II Reflex Sight
The EZ Finder II reflex sight (Figure 4) makes pointing your
telescope almost as easy as pointing your finger! It’s a non-
magnifying aiming device that superimposes a tiny red dot
on the sky, showing exactly where the telescope is pointed.
The EZ Finder II works by projecting a tiny red dot (it’s not a
laser beam) onto a lens mounted in the front of the unit.
When you look through the EZ Finder II, the red dot will
appear to float in space, helping you locate even the faintest
of deep space objects. The red dot is produced by a light-
emitting diode (LED) near the rear of the sight. A 3-volt lithi-
um battery provides the power for the diode.
Turn the power knob clockwise until you hear the “click” indi-
cating that power has been turned on. Look through the back
of the reflex sight with both eyes open to see the red dot.
Position your eye at a comfortable distance from the back of
the sight. The intensity of the dot is adjusted by turning the
power knob. For best results when stargazing, use the
dimmest possible setting that allows you to see the dot with-
out difficulty. Typically a dimmer setting is used under dark
skies and a bright setting is used under light-polluted skies
or daylight.
At the end of your observing session, be sure to turn the
power knob counterclockwise until it clicks off. When the two
white dots on the EZ Finder II’s rail and power knob are lined
up, the EZ Finder II is turned off.
Aligning the EZ Finder II Reflex Sight
When the EZ Finder II is properly aligned with the telescope,
an object that is centered on the EZ Finder II’s red dot
should also appear in the center of the field of view of the
telescope’s eyepiece. Alignment of the EZ Finder II is easiest
during daylight, before observing at night. Aim the telescope
at a distant object such as a telephone pole or roof chimney
and center it in the telescope’s eyepiece. The object should
be at least 1/2 mile away. Now, with the EZ Finder turned on,
Figure 4. The EZ Finder II reflex sight.
Naked-eye view
Figure 5. The view through a reflector telescope is upside down.
Altitude
adjustment
knob
Mounting
bracket
Azimuth
adjustment
knob
Power
knob
View through telescope

7
look though the EZ Finder II. The object will appear in the
field of view near the red dot.
Note: The image in the main telescope will appear
upside-down (rotated 180°). This is normal for reflector
telescopes (Figure 5).
Without moving the main telescope, use the EZ Finder II’s
azimuth (left/right) and altitude (up/down) adjustment knobs
to position the red dot on the object in the eyepiece.
When the red dot is centered on the distant object, check to
make sure that the object is still centered in the telescope’s
field of view. If not, recenter it and adjust the EZ Finder II’s
alignment again.When the object is centered in the eyepiece
and on the EZ Finder’s red dot, the EZ Finder II is properly
aligned with the telescope.
The EZ Finder II alignment should be checked before every
observing session. Choose any bright star or planet, center
the object in the telescope’s eyepiece, then adjust the knobs
until the object is centered on the red dot of the EZ Finder.
Typically, only minimal adjustments will be needed, even if
the EZ Finder II is removed from its bracket.
5. Setting Up and Using the
Equatorial Mount
When you look at the night sky, you no doubt have noticed
that 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 eas-
ily “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 (R.A.) 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, or Polaris. It lies within 1°of the north celes-
tial pole (NCP), which is an extension of the Earth’s rotation-
al axis out into space. Stars in the Northern Hemisphere
appear to revolve around the NCP.
To find Polaris in the sky, look north and locate the pattern of
the Big Dipper (Figure 6). 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 bare-
ly visible with the naked eye (magnitude 5.5).
To polar-align the ShortTube 4.5 EQ:
1. Level the equatorial mount by adjusting the length of the
three tripod legs.
2. Loosen the latitude lock T-bolt. Turn the latitude adjust-
ment T-bolt and tilt the mount until the pointer on the lati-
tude 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 dis-
tance away.
3. Loosen the Dec. lock knob and rotate the telescope opti-
cal tube until it is parallel with the R.A. axis, as it is in
Figure 6. 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 five times the distance between those stars and you’ll reach Polaris, which lies within 1°of the north
celestial pole (NCP).
Big Dipper
(in Ursa Major)
Little Dipper
(in Ursa Minor)
N.C.P.
PointerStars
Polaris
Cassiopeia

8
Figure 1. The pointer on the Dec. setting circle should
read 90°. Retighten the Dec. lock lever.
4. Loosen the azimuth lock knob at the base of the equatori-
al mount and rotate the mount so the telescope tube (and
R.A. axis) points roughly at Polaris. If you cannot see
Polaris directly from your observing site, consult a com-
pass and rotate the mount so the telescope points North.
Retighten the azimuth lock knob.
The equatorial mount is now polar aligned.
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
undo the polar alignment. The telescope should be moved
only about its R.A. and Dec. axes.
Use of the R.A. and Dec.
Slow-Motion Control Cables
The R.A. and Dec. slow-motion control cables allow fine
adjustment of the telescope’s position to center objects with-
in the field of view. Before you can use the cables, you must
manually “slew”the mount to point the telescope in the vicini-
ty of the desired target. Do this by loosening the R.A. and
Dec. lock knobs and moving the telescope about the mount’s
R.A. and Dec. axes. Once the telescope is pointed some-
where close to the object to be viewed, retighten the mount’s
R.A. and Dec. lock knobs.
The object should now be visible somewhere in the EZ
Finder II. If it isn’t, use the slow-motion controls to scan the
surrounding area of sky. When the object is visible in the EZ
Finder II, use the slow-motion controls to center it. Now, look
in the telescope’s eyepiece. If the EZ Finder II is properly
aligned, the object should be visible somewhere in the field
of view. Once the object is visible in the eyepiece, use the
slow-motion controls to center it in the field of view.
The Dec. slow-motion control cable can move the telescope
a maximum of 25°. This is because the Dec. slow-motion
mechanism has a limited range of mechanical travel. (The
R.A. slow-motion mechanism has no limit to its amount of
travel.) If you can no longer rotate the Dec. control cable in a
desired direction, you have reached the end of travel, and
the slow-motion mechanism must be reset. This is done by
first rotating the control cable several turns in the opposite
direction from which it was originally being turned. Then,
manually slew the telescope closer to the object you wish to
observe (remember to first loosen the Dec. lock knob). You
should now be able to use the Dec. slow-motion control
cable again to fine adjust the telescope’s position.
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 cable clockwise. The Dec. slow-
motion control cable is not needed for tracking. Objects will
appear to move faster at higher magnifications, because the
field of view is narrower.
Optional Electronic Drives for Automatic
Tracking
An optional DC electronic drive can be mounted on the R.A.
axis of the equatorial mount to provide hands-free tracking.
Objects will then remain stationary in the field of view without
any manual adjustment of the R.A. slow-motion control
cable.
Understanding the Setting Circles
The setting circles on an equatorial mount enable you to
locate celestial objects by their “celestial 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 lati-
tude. The R.A. and Dec. values for celestial objects can be
found in any star atlas or star catalog.
The mount’s R.A. setting circle is scaled in hours, from 1
through 24, with small marks in between representing 10-
minute increments. The numbers closest to the R.A. axis
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 mark
representing 2.5°increments. Values of Dec. coordinates
range from +90°to -90°. The 0°mark indicates the celestial
equator. When the telescope is pointed north of the celestial
equator, values of the Dec. setting circle are positive, while
when the telescope is pointed south of the celestial equator,
values of the Dec.setting circle are negative.
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 (there are 60 arc-
minutes in 1 degree of declination).
Before you can use the setting circles to locate objects, the
mount must be correctly polar aligned, and the R.A. setting
circle must be calibrated. The Dec. setting circle has been
permanently calibrated at the factory, and should read 90°
whenever the telescope optical tube is parallel with the R.A.
axis.
Calibrating the Right Ascension Setting Circle
1. Identify a bright star in the sky near the celestial equator
(Dec. = 0°) and look up its coordinates in a star atlas.
2. Loosen the R.A. and Dec. lock knobs on the equatorial
mount, so the telescope optical tube can move freely.
3. Point the telescope at the bright star whose coordinates
you know. Lock the R.A. and Dec. lock knobs. Center the
star in the telescope’s field of view with the slow-motion
control cables.
4. Rotate the setting circle until the metal arrow indicates
the R.A. coordinate listed in the star atlas for the object.

Finding Objects With the Setting Circles
1. Now that both setting circles are calibrated, look up in a
star atlas the coordinates of an object you wish to view.
2. Loosen the Dec. lock knob and rotate the telescope until
the Dec. value from the star atlas matches the reading on
the Dec. setting circle. Remember that values of the Dec.
setting circle are positive when the telescope is pointing
north of the celestial equator (Dec. = 0°), and negative
when the telescope is pointing south of the celestial
equator. Retighten the lock knob.
3. Loosen the R.A. lock knob and rotate the telescope until
the R.A. value from the star atlas matches the reading on
the R.A. setting circle. Remember to use the upper set of
numbers on the R.A. setting circle. Retighten the lock
knob.
Most setting circles are not accurate enough to put an object
dead-center in the telescope’s eyepiece, but they should
place the object somewhere within the field of view of the EZ
Finder II, assuming the equatorial mount is accurately polar
aligned. Use the slow-motion controls to center the object in
the EZ Finder II, and it should appear in the telescope’s field
of view.
The R.A. setting circle must be re-calibrated 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 down-
ward. But it will not look like that when the telescope is point-
ed 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 lat-
itude adjustment T-bolt. 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 knob
and rotate the telescope on the R.A. axis until the counter-
weight shaft is horizontal (parallel to the ground). Then
loosen the Dec. lock knob and rotate the telescope until it is
pointing straight overhead. The counterweight shaft is still
horizontal.Then retighten both lock knobs.
Similarly, to point the telescope directly south, the counter-
weight 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 counter-
weight 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 direc-
tions, 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.
Figure 7 illustrates how the telescope will look pointed at the
four cardinal directions—north, south, east, and west
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!
6. Collimating the Optics
Collimating is the process of adjusting the mirrors so they
are aligned with one another. 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 the peak performance of
your telescope, so it should be checked regularly. Collimating
is relatively easy to do and can be done in daylight.
To check collimation, remove the eyepiece and look down
the focuser drawtube. You should see the secondary mirror
centered in the drawtube, as well as the reflection of the pri-
9
Figure 7. This illustration show the telescope pointed in the four cardinal directions (a) north (b) south (c) east (d) west. Note that the
tripod and mount have not been moved; only the telescope tube has been moved in the R.A. and Dec. axes.
abcd

10
mary mirror centered in the sec-
ondary mirror, and the reflection
of the secondary mirror (and your
eye) centered in the reflection of
the primary mirror, as in Figure
8a. If anything is off-center, pro-
ceed with the following collimat-
ing procedure.
The Collimation Cap and
Mirror Center Mark
Your ShortTube 4.5 EQ comes
with a collimating cap. This is a
simple cap that fits on the
focuser drawtube like a dust cap,
but has a hole in the center and a
silver bottom. This helps center
your eye so that collimating is
easy to perform. Figures 8b
through 8e assume you have the
collimation cap in place.
In addition to providing the colli-
mation cap, you’ll notice a tiny
ring (sticker) in the exact center
of the primary mirror. This “center
mark”allows you to achieve a
very precise collimation of the
primary mirror; you don’t have to
guess where the center of the
mirror is. You simply adjust the
mirror position (described below)
until the reflection of the hole in
the collimation cap is centered
inside the ring.
NOTE: The center ring sticker
need not ever be removed
from the primary mirror.
Because it lies directly in the
shadow of the secondary mir-
ror, its presence in no way
adversely affects the optical
performance of the telescope
or the image quality. That
might seem counterintuitive,
but it’s true!
Aligning the Secondary
Mirror
With the collimation cap in place,
look through the hole in the cap
at the secondary (diagonal) mirror. Ignore the reflections for
the time being. The secondary mirror itself should be cen-
tered in the focuser drawtube, in the direction parallel to the
length of the telescope. If it isn’t, as in Figure 8b, it must be
adjusted.Typically, this adjustment will rarely, if ever, need to
be done. 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 wall.Placing a piece of white paper in
the telescope tube opposite the
focuser (i.e., on the other side of
the secondary mirror) will also be
helpful in collimating the second-
ary mirror. Using a 2.5mm Allen
wrench, loosen the three small
alignment setscrews in the cen-
ter hub of the 3-vaned spider
several turns. Now hold the mir-
ror holder stationary (be careful
not to touch the surface of the
mirrors), while turning the center
screw with a Phillips head screw-
driver (Figure 9). Turning the
screw clockwise will move the
secondary mirror toward the
front opening of the optical tube,
while turning the screw counter-
clockwise will move the second-
ary mirror toward the primary
mirror.
When the secondary mirror is
centered in the focuser draw-
tube, rotate the secondary mirror
holder until the reflection of the
primary mirror is as centered in
the secondary mirror as possible.
It may not be perfectly centered,
but that is OK. Now tighten the
three small alignment screws
equally to secure the secondary
mirror in that position.
If the entire primary mirror reflec-
tion is not visible in the second-
ary mirror, as in Figure 8c, you
will need to adjust the tilt of the
secondary mirror.This is done by
alternately loosening one of the
three alignment setscrews while
tightening the other two, as
depicted in Figure 10.The goal is
to center the primary mirror
reflection in the secondary mir-
ror, as in Figure 8d. Don’t worry
that the reflection of the second-
ary mirror (the smallest circle,
with the collimation cap “dot”in
the center) is off-center. You will
fix that in the next step.
Aligning the Primary Mirror
The final adjustment is made to the primary mirror. It will
need adjustment if, as in Figure 8d, 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 the “dot”of the colli-
mation cap) is off-center.
Figure 8. 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 under the focuser, but it needs to be adjusted
(tilted) so that the entire primary mirror is visible. (d) The
secondary mirror is correctly aligned, but the primary mirror
still needs adjustment.When the primary mirror is correctly
aligned, the “dot”will be centered, as in (e).
a.
b. c.
d. e.