INSTRUCTION MANUAL
IN 165 Rev. B 09/03
Providing Exceptional Consumer Optical Products Since 1975
Customer Support (800) 676-1343
E-mail: support@telescope.com
Corporate Offices (831) 763-7000
P.O. Box 1815, Santa Cruz, CA 95061
Orion
®
SkyQuest XT6&XT8
#9806 and #9808 Dobsonian Reflecting Telescopes
Secondary mirror with
4-vane spider (not shown)
Navigation knob
Right side panel
Front brace
Handle
Top baseplate
Ground baseplate
2
Figure 1.
The SkyQuest XT Dobsonian (XT6 pictured)
Finder scope
Finder scope bracket
Eyepiece
Focus knob
Optical tube
Altitude side bearing
CorrecTension Friction
Optimization System
Pull loop
Left side panel
Eyepiece rack
3
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.
Welcome to an exciting new world of adventure! Your
SkyQuest Dobsonian is a high-quality optical instrument
designed to bring you dazzling views of the outer reaches
of our universe.Easy enough for kids to use, and portable
enough for anyone to carry, the SkyQuest will provide fun
and entertainment for the entire family. Whether you are
brand-new to amateur astronomy or a seasoned stargazer, get ready for many evenings of enjoyment and
fascination. Before venturing into the night with your new
telescope, we recommend that you read through this
instruction manual.Not only does it provide accurate directions for assembly and use, b ut it also serves as a guide for
your first explorations in the sky.
Table of Contents
1. Unpacking . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
2. Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
3. Using Your Telescope . . . . . . . . . . . . . . . . . . . .7
4. Collimation (Aligning the Mirrors) . . . . . . . . . .10
5. Astronomical Observing . . . . . . . . . . . . . . . . .12
6. Care and Maintenance . . . . . . . . . . . . . . . . . .16
7. Specifications . . . . . . . . . . . . . . . . . . . . . . . . .17
1. Unpacking
The telescope will arrive in two box es, one containing the optical tube assembly and accessories, the other containing the
unassembled Dobsonian base. Be careful unpacking the
boxes. We recommend keeping the original shipping 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 below 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.
Parts List
Box #1: Optical Tube Assembly and Accessories
Qty. Description
1 Optical tube assembly
1 Dust cover
1 25mm Sirius Plössl eyepiece, 1.25" barrel diameter
1 10mm Sirius Plössl eyepiece, 1.25" barrel diameter
1 6x30 finder scope
1 Finder scope bracket with O-ring
1 Collimation cap
1 Eyepiece rack
2 Eyepiece rack mounting wood screws (length 3/4")
2 Spring coils
2 Pull loops
4 Nylon spacers (black)
2 1/4" washers (black)
2 Phillips-head screws (black, length 1-3/4")
2 Screws with round knob attached
Box #2: Dobsonian Base
Qty. Description
1 Left panel
1 Right panel
1 Front brace
1 Top baseplate
1 Ground baseplate
12 Base assembly screws (length 2")
1 Hex key (size 4mm)
3 Plastic feet
3 Feet attachment wood screws (length 1")
1 Self-adhesive rubber bumper
1 Large hex-head bolt (length 3")
2 3/8" washers
1 3/8" lock nut
1 Nylon spacer (white)
1T-nut
1 Handle
2 Socket-head cap screws, 5/16" (black)
2 5/16" washers (black)
2 5/16" nuts (black)
1 Hex key (6mm)
4
2. Assembly
Now that you have unpacked the boxes and familiarized yourself with all the parts in front of you, it’s time to begin
assembly. The optics of the telescope are already installed in
the tube, so most of the required assembly concerns the
Dobsonian base.
Assembly of the Dobsonian base
Refer to Figure 2 during base assembly. The base need only
be assembled once, unless you disassemble it for long-ter m
storage.The assembly process takes about 15 minutes and
requires a Phillips screwdriver, an adjustable crescent
wrench, and the provided hex keys.
Note: When tightening screws, tighten them until firm,
but be careful not to strip the holes by over-tightening.
If you use an electric screwdriver, do final tightening
with a standard screwdriver to avoid stripping.
1. Screw the plastic feet into the underside of the ground
baseplate (A) using the self-tapping wood screws provided, with a Phillips screwdriver. Insert the screws through
the feet and thread them into the predrilled starter holes.
2. Loosely attach the front brace (B) to the two side panels
(C) with six of the base assembly screws in the predrilled
holes. Use the 4mm hex key to tighten the screws.The
side panels should be oriented so the SkyQuest label is
facing outward.The front brace should be oriented so the
index mark is facing inwards.Do not completely tighten the
screws yet.
3. Attach the two sides (C) with the front brace attached to
the top baseplate (D) with the remaining six base assembly screws in the predrilled holes.Tighten all six screws.
4. Tighten the six side panel screws installed earlier.
5. Insert the white nylon bushing (E) into the hole in the center of the top baseplate (D).Tap the nylon bushing in so it
goes all the way into the top baseplate.The nylon bushing
should be flush with the top surface of the top baseplate.
6. Insert the T-nut (K) into the center hole of the ground baseplate (A) so the nut’s flanged top is on the same side of the
baseplate as the Teflon pads. Thread the large hex-head
bolt (G) with a 3/8" washer (F) attached up through the
ground baseplate and through the T-nut until it is tight.Now
position the top baseplate (D) (with side panels attached)
over the ground baseplate and lower it so the bolt goes
through the nylon spacer in the center hole of the top baseplate. Now thread the remaining 3/8" washer (H) and lock
nut (I) onto the bolts shaft.You might need to hold the bolts
head in place with another crescent wrench or pliers.
Tighten the lock nut with the wrench just enough to allow a
slight separation of the top and bottom baseplates when
the mount is lifted.The purpose of the lock nut is merely to
keep the two baseplates from coming apart when moving
the telescope.
Note: Over tightening the lock nut (I) will make the mount
difficult to rotate in the azimuthal (horizontal) direction.
7. Attach the handle (J) to the front brace (B) with the two
black socket-head screws. Insert the screws through the
handle and into the predrilled holes. Place the 5/16" washers and 5/16" nuts on the protruding ends of the screws.
Tighten the nuts with a crescent wrench while holding the
bolts stationary with the 6mm hex key.
8. The rubber bumper (L) provides a convenient “stop” for the
telescope’s altitude motion;it prevents the telescope mirror
cell from being knocked against the hard surface of the
base’s front brace. At the bottom of the interior surface of
the front brace, you will notice a small index mark
engraved. Remove the backing from the rubber bumper
and position the bumper over the index mark, as shown in
Figure 2. Exploded view of the SkyQuest XT Dobsonian base.
Figure 3. Position the rubber bumper “stop”over the index mark on
the inside surface of the front brace.
C
C
B
L
I
J
D
A
H
E
K
F
G
5
Figure 3. Press firmly so the adhesive holds the bumper
securely in place.
Installing the Eyepiece Rack
The aluminum eyepiece rack is a standard accessory on
SkyQuest Dobsonians. On the XT6 it holds three 1.25" eyepieces in a convenient place on the base;on the XT8 it holds
three 1.25" eyepieces and one 2" eyepiece.These eyepieces
will be within easy reach while you’re observing.The rack will
also hold a 1.25" barlow lens.About halfway down the left side
panel of the base you will notice two predrilled starter holes,
about 6" apart. Take the black wood screws and thread them
into the starter holes with a Phillips screwdriver.Then you can
“keyhole”the eyepiece rack onto the wood screws and continue tightening the screws (Figure 4). If you want to be able to
remove the rack, do not tighten the screws too tightly. Be certain that the screws are loose enough that you can lift the rack
and remove it from the screws through the larger part of the
keyhole. If you want to have the rack permanently attached,
thread the screws tightly.
Placing the Optical Tube on the Dobsonian Base
Lift the optical tube and set the altitude bearings on either side
of the tube in the “cradle” of the base (Figure 5). The unique
flange design of the altitude bearing allows for automatic leftto-right centering of the optical tube in the cradle. Once in the
cradle, the tube should pivot freely up and down with gentle
hand pressure. Note that the tube will not yet be properly balanced, since the eyepiece and finder scope are not in place,
and the CorrecTension system has not been installed.
Installing the Finder Scope
The SkyQuest XT6 & 8 come with a high quality, 6x30 achromatic finder scope (Figure 6a). The “6” means it magnifies 6
times, the “30”means it has a 30mm diameter lens.
To place the finder scope in the finder scope bracket, first
unthread the two black nylon screws until the screw ends are
flush with the inside diameter of the bracket.Place the O-ring
that comes on the base of the bracket over the body of the
finder scope until it seats into the groove on the middle of the
finder scope.Slide the eyepiece end (narrow end) of the finder
scope into the end of the bracket’s cylinder that does not have
the alignment screws while pulling the chrome, spring-loaded
tensioner on the bracket with your fingers (see Figure 6b).
Push the finder scope through the bracket until the O-ring
seats just inside the front opening of the bracket’s cylinder.
Now, release the tensioner and tighten the two black nylon
screws a couple of turns each to secure the finder scope in
Figure 4. Using the two supplied screws, install the aluminum
eyepiece rack in the predrilled holes about halfway down the left
side panel of the base. (XT6 eyepiece rack shown)
Figure 5. Set the optical
tube on the “cradle” of the
base so that the altitude side
bearings on the tube rest on
the white plastic “pads.”
Figure 6a. The 6x30 finder
scope.
Figure 6b. Inserting the
finder scope into the finder
scope bracket
Focus
lockring
Tensioner
Objective lens
Finder
Scope Bracket
Alignment thumbscrews
6
place.The tips of the tensioner and nylon screws should seat
into the wide groove on the rear of the finder scope’s body.
Slide the base of the finder scope bracket into the dovetail
holder near the focuser .Lock the bracket into position by tightening the knurled thumbscrew on the dovetail holder.
Installing the CorrecTension (XT) Friction
Optimization System
Perhaps the most exciting new feature of the SkyQuest
Dobsonians is the CorrecTension Friction Optimization system.Because of their light weight, 6" and 8" Dobsonians have
always been plagued by insufficient friction on the altitude
bearing surfaces. As a result, such telescopes move up and
down much too freely.This causes problems when the observer tries to accurately center and track an object for viewing,
especially at higher powers.Also, the telescope becomes very
sensitive to balance, requiring additional equipment such as
counterweight systems or adjustable side bearings to compensate.
SkyQuest Dobsonians employ a simple yet effective remedy
for the friction problem that obviates the need for such cumbersome countermeasures. CorrecTension Friction Optimization
utilizes a spring coil to “pull”the tube assembly down onto the
altitude bearing pads, thereby increasing the friction by just
the right amount. With CorrecTension, you can change eyepieces, or add a barlow lens or solar filter without having to
tediously adjust the telescope’s balance as you would with
other Dobsonians.The altitude friction will roughly equal the
azimuth friction, ensuring optimal performance.
To install the CorrecTension assembly, follow these steps
while referring to Figure 7:
1. Put one of the black nylon spacers on a black Phillips-head
screw. The spacer should be oriented so the narrow end
seats against the head of the screw. Slip one of the black
1/4" washers over the end of the screw. Now, thread the
screw into the hole in the base side panel just below the
cradle.The screw will thread into the preinstalled inser t in
the hole. Use a Phillips screwdriver to tighten the screw.
Repeat this procedure on the opposite side panel.
2. Next, insert one of the screws with a round plastic knob
attached through the end ring of one of the springs. Slip a
black nylon spacer onto the screw. Orient the spacer so
the narrow end is closest to the knob.Thread the entire
assembly into the hole in the center of the telescope’s altitude side bearing until tight. The end ring of the spring
should seat onto the narrow end of the spacer.Repeat this
procedure for the other altitude side bearing.
3 Attach a pull loop to the free end of each spring. Slide the
loop through the opening in the ring on the end of the spring.
4. Now, pull each spring down using the pull loop, and position the spring’s end ring over the head of the Phillips
screw (installed in Step 1) and onto the narrow part of the
nylon spacer, as shown in Figure 8. You needn’t attach
both springs simultaneously; one at a time is fine.
Figure 7. Close-up view of the CorrecTension system, which
pulls the tube assembly down onto the altitude bearing pads.
Black nylon
spacers
1/4" washer
(black)
Altitude side bearing
Screw w/round knob
Spring
Phillips-head
screw (black)
Pull loop
Figure 8. (a) To attach the spring to the base, grip the pull loop
with your index finger and pull down on the spring.(b) While pulling
down, slip the end ring of the spring over the bolt head and onto the
narrow part of the nylon spacer, then release the pull loop.
a.
b.
Focusing the Telescope
Insert the low-power 25mm eyepiece into the focuser and
secure with the thumbscrew(s). 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
just starts to blur again, then reverse the rotation of the knob,
just to make sure you’ve hit the exact focus point.
If you have trouble focusing, rotate the focusing knob so the
drawtube is in as far as it will go. Now look through the eyepiece while slowly rotating the focusing knob in the opposite
direction. You should soon see the point at which focus is
reached.
The focuser of the XT8 features a drawtube lock knob.There
are times when you may want to lock the drawtube to preserve the focus setting.This is done by turning the focus lock
knob clockwise until it is tight.The focus setting will now be
locked.When you need to adjust the focus again, be sure to
loosen the lock knob.
The XT6 does not have a f ocus lock;instead it has a drawtube
tension thumbscrew. It will not lock the drawtube in place, but
it can be used to increase or decrease the amount of tension
on the drawtube.If you feel the drawtube is moving too loosely when you turn the focusing knob, or if focusing feels too
tight, make adjustments by turning the thumbscrew. Do not
loosen it too much as there must be some tension to keep the
drawtube secure in the focuser.
Aligning the Finder Scope
The finder scope must be aligned accurately with the telescope for proper use.To align it, first aim the main telescope
7
The CorrecTension system is now installed and engaged. If
you wish to remove the telescope from the base, you will first
need to disconnect the springs from the “posts” on the
Dobsonian base.The springs will remain captive on the altitude side bearings, so they will not get lost.
Inserting an Eyepiece
The final step in the assembly process is to insert an eyepiece
into the telescope’s focuser.Take the cover cap off the end of
the focuser drawtube.
For the XT6: Loosen the two thumbscrews on the eyepiece
holder and insert one of the eyepieces.Then secure it in place
with the thumbscrews.The other eyepiece can be placed in
the eyepiece rack until it is needed.
For the XT8: There are three thumbscrews on the focuser,
one holds the eyepiece, and two hold the 1.25" adapter. To
insert the eyepiece, loosen the thumbscrew that is on the
1.25" adapter itself (it will be highest up on the focuser).
Insert the eyepiece into the adapter and secure it by tightening the thumbscrew.
The assembly of your SkyQuest Dobsonian is now complete.
It should appear as in Figure 1.The dust cover on the front of
the telescope should always remain in place when the telescope is not in use.It is also a good idea to store eyepieces in
an eyepiece case and to replace the cover cap on the focuser
when the telescope is idle.
3. Using Your Telescope
It is best to get a feel for the basic functions of the SkyQuest
Dobsonian during the day, before observing astronomical
objects at night.This way you will not have to fumble around
trying to orient yourself in the dark! Find a spot outdoors
where you have plenty of room to mo ve around the telescope,
and where you have a clear view of some object or vista that
is at least 1/4-mile away. It is not critical that the base be
exactly level, but it should be placed on somewhat flat ground
or pavement to ensure smooth movement of the telescope.
Remember, never point the telescope at or near the
Sun without using a proper solar filter over the front
aperture!
Altitude and Azimuth
The Dobsonian base of the SkyQuest permits motion of the
telescope along two axes: altitude (up/down) and azimuth
(left/right) (Figure 9). This is very convenient, since up/down
and left/right are the most “natural”ways that people aim.As a
result, pointing the telescope is exceptionally easy.
Simply take hold of the navigation knob and move it left or
right so the base rotates about its central azimuth bolt, and
move it up or down so the altitude side bearings rotate in the
base’s cradle. Both motions can be made simultaneously and
in a continuous manner for easy aiming.Move the telescope
gently—let it glide. In this way you can point the telescope to
any position in the night sky, from horizon to horizon.
Figure 9. The SkyQuest has two axes of motion:altitude
(up/down) and azimuth (left/right).
Azimuth
Altitude
8
in the general direction of an object at least 1/4-mile away the top of a telephone pole, a chimney, etc. Position that
object in the center of the telescope’s eyepiece.
Now, look in the finder scope. Is the object visible? Ideally, it
will be somewhere in the field of view. If it is not, some coarse
adjustments of the two finder scope alignment thumbscrews
will be needed to get the finder scope roughly parallel to the
main tube.
Note:The image in both the finder scope and the main telescope will appear upside-down (rotated 180°).This is normal
for finder scopes and reflector telescopes.(see Figure 10)
With the image in the finder scope’s field of view, use the two
alignment thumbscrews to center the object in the intersection
of the crosshairs.
By turning the alignment thumbscrews, you change the line of
sight of the finder scope. Continue making adjustments to the
alignment thumbscrews until the images in both the finder
scope and the telescope’s eyepiece are exactly centered.
Check the alignment by moving the telescope to another
object and fixing the finder scope’s crosshairs on the exact
point you want to look at.Then look through the telescope’s
eyepiece to see if that point is centered in the field of view. If it
is, the job is done. If not, make the necessary adjustments to
the finder scope alignment thumbscrews until the two images
match up.
The finder scope alignment needs to be checked before every
observing session. This can easily be done at night, before
viewing through the telescope.Choose any bright star or planet, center the object in the telescope eyepiece, and then
adjust the finder scope alignment thumbscrews until the star
or planet is also centered on the finder’s crosshairs.The find-
er scope is an invaluable tool for locating objects in the night
sky;its usage for this purpose will be discussed later, in detail.
Focusing the Finder Scope
If, when looking through the finder scope, the images appear
somewhat out of focus, you will need to refocus the finder
scope for your eyes. Loosen the lock ring located behind the
objective lens cell on the body of the finder scope (see Figure
6a). Back the lock ring off by a few turns, for now.Refocus the
finder scope on a distant object by threading the objective
lens cell in or out on the finder scope body. Precise focusing
will be achieved by focusing the finder scope on a bright star.
Once the image appears sharp, retighten the lock ring behind
the objective lens cell. The finder scope’s focus should not
need to be adjusted again.
Aiming/Pointing the Telescope
Now that the finder scope is aligned, the telescope can be
quickly and accurately pointed at anything you wish to
observe.The finder scope has a much wider field of view than
the telescope’s eyepiece, and therefore it is much easier to
first center an object in the finder scope. Then, if the finder
scope is accurately aligned, the object will also be centered in
the telescope’s field of view.
Start by once again moving the telescope until it is pointed in
the general direction of the object you want to see. Some
observers find it convenient to sight along the tube to do this.
Now, look in the finder scope. If your general aim is accurate,
the object should appear somewhere in the finder scope.
Make small adjustments to the telescope’s position until the
object is centered on the finder’s crosshairs.Now, look in the
telescope’s eyepiece and enjoy the view!
Magnification
Once the object you want to view is well-centered in the
25mm eyepiece, you may want to increase the magnification
to get a closer view .Loosen the thumbscrew(s) on the focuser
drawtube and remove the eyepiece. Place it in the eyepiece
rack, if you wish.Insert the 10mm eyepiece in the focuser then
tighten the thumbscrew(s).If you were careful not to bump the
telescope, the object should still be centered within the field of
view. Notice that the object being viewed is now larger, but
somewhat dimmer.
The SkyQuest is designed to accept any eyepiece with a barrel diameter of 1.25".The XT8 can also accept 2" 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)
Magnification=
Eyepiece Focal Length (mm)
The 6” and 8” SkyQuest Dobsonians both have a focal length
of 1200mm. So, the magnification with the supplied 25mm eyepiece is:
Naked-eye view
View through finder scope and telescope
Figure 10. The view through a standard finder scope and
reflector telescope is upside down.This is true for the SkyQuest
and its finder scope as well.
9
1200mm
= 48x
25mm
The magnification provided by the 10mm eyepiece is
1200mm
= 120x
10mm
The maximum attainable magnification for a telescope is directly
related to how much light its optics can collect.A telescope with
more light-collecting area, or aperture, can yield higher magnifications than a smaller aperture telescope. The maximum
practical magnification for any telescope, regardless of optical
design, is about 60x per inch of aperture.This translates to about
360x for the SkyQuest XT6 and 480x for the XT8.
Keep in mind that as magnification is increased, the brightness
of the object being viewed will decrease; this is an inherent
principle of the physics of optics and cannot be avoided. If
magnification is doubled, an image appears four times dimmer.If magnification is tr ipled, image brightness is reduced by
a factor of nine!
Note About High Magnifications:
Maximum magnifications are achieved only under the most
ideal viewing conditions at the best observing sites. Most of
the time, magnifications are limited to 200x or less, regardless
of aperture. This is because the Ear th’s atmosphere distorts
light as it passes through. On nights of good “seeing,” the
atmosphere will be still and will yield the least amount of distortion. On nights of poor seeing, the atmosphere will be
turbulent, which means different densities of air are rapidly
mixing.This causes significant distortion of the incoming light,
which prevents sharp views at high magnifications.
Tube Balance
Dobsonians are designed to balance with standard supplied
accessories, such as an eyepiece and a finder scope.But what
if you want to use a larger finder scope or a heavier eyepiece?
The telescope will no longer be properly balanced, and will not
hold its position properly.This makes the telescope difficult to
use, since it is critical that it hold its position (when not purposefully moved) to keep objects centered in the field of vision.
Traditional Dobsonian designs expect the user to compensate
for heavier accessories by adding weight to the opposite end
of the telescope tube. Such counterweighting systems can be
expensive and unwieldy. The CorrecTension Friction
Optimization system of the SkyQuest Dobsonians, however,
solves the finicky balance problem.The spr ing coils pull the
tube down onto the base, thereby increasing the friction on the
altitude bearing pads.With CorrecTension, the added weight
of small front-end loads will not adversely affect the balance of
the telescope.
If you install an array of heavier accessories onto your
SkyQuest’s optical tube, you may need at some point to counterbalance the telescope with a counterweight system.
Carrying the Telescope
Moving the SkyQuest is easy to do.Because the spr ings of the
CorrecTension system hold the optical tube captive on the base,
the entire telescope can be carried as one unit. This requires
some caution, however.If the telescope is lifted improperly, the
front of the tube could swing down and hit the ground.
First, point the optical tube straight up (vertical). Remove any
eyepieces from the telescope and eyepiece rack, and place
them in an eyepiece case.Grasp the handle on the front of the
base with one hand while supporting the telescope tube vertically with the other (see Figure 11). Now, lift the telescope
from the handle. Once the telescope is in the horizontal position, you can carry the entire unit with one hand. The handle
position properly balances the load for easy carrying.
Figure 11. Picking up and
carrying the SkyQuest as a
single unit (with tube held
captive on the base) requires
some caution. (a) First,
position the tube vertically.
Then, grasp the handle on the
base with one hand while
supporting the tube with the
other.(b) With knees bent,
slowly lift the base while
supporting the tube with one
hand.This ensures that the
tube will not swing down and
impact the ground. (c) As you
lift, the whole assembly will tilt
down, becoming nearly
parallel with the ground, at
which time you can let go of
the tube with your supporting
hand. Make sure you are
comfortable with the weight of
the whole assembly before
attempting to carry it!
a.
b.
c.
ondary mirror (and your eye) centered in the reflection of the primary mirror, as in Figure 12a. If anything is off-center, as in
Figure 12b, proceed with the follo wing collimation procedure .
The Collimation Cap and Mirror Center Mark
Your SkyQuest XT comes with a collimation 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 collimation is easy to perform. Figures 12b
through 12e assume you have the collimation cap in place .
In addition to providing the collimation 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. This center mark is also
required for best results with other collimating devices, such
as Orion’s LaserMate Laser Collimator, obviating the need to
remove the primary mirror and mark it yourself.
Note:The center ring sticker need not ever be removed
from the primary mirror. Because it lies directly in the
shadow of the secondary mirror, 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!
If you wish to carry the optical tube and base separately, simply disengage the CorrecTension springs by unhooking them
from the posts on the base, using the pull loops.The springs
remain captive on the telescope side bearings. Now the base
and tube are disengaged and can be transported separately.
Do not use the navigation knob as a carry handle!
Note:The SkyQuest may be too heavy for some users to
lift and carry as one unit. Do not strain yourself! If the
load seems too heavy, disengage the springs and carry
the base and tube separately.
When putting the SkyQuest into a vehicle, common sense prevails. It is especially impor tant that the optical tube does not
knock around;this can cause the optics to become misaligned,
and could dent the tube.We recommend transporting and storing the tube assembly in a padded case for proper protection.
4. Collimation
Collimation is the process of adjusting the mirrors so they are
correctly 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. Collimation is relatively easy to do and can be done in daylight.
To check collimation, remove the eyepiece and look down the
focuser drawtube .Y ou should see the secondary mirror centered
in the drawtube, as well as the reflection of the primary mirror
centered in the secondary mirror, and the reflection of the sec-
10
Figure 12. 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.
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 secondar y mirror itself should be centered in the focuser drawtube, in the direction parallel to the
length of the telescope. If it isn’t, as in Figure 12b, it must be
adjusted.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 secondary mirror. Using a 2mm hex key, loosen the three small
alignment set screws in the center hub of the 4-vaned spider
several turns.Now hold the mirror holder stationary (be careful not to touch the surface of the mirrors), while turning the
center screw with a Phillips head screwdriver (see Figure 13).
Tur ning 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 secondary mirror
toward the primary mirror.
Note:When making these adjustments, be careful not to
stress the spider vanes or they may bend.
When the secondary mirror is centered in the focuser drawtube, rotate the secondary mirror holder until the reflection of
the primary mirror is as centered in the secondar y 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
reflection is not visible in the secondary mirror, as in Figure
12c, 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 14.The goal is to center the primary mirror reflection in
the secondary mirror, as in Figure 12d. Don’t worr y that the
reflection of the secondary mirror (the smallest circle, with the
collimation cap “dot”in the center) is off-center.Y ou 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 12d, 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 collimation
cap) is off-center.
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 star t, turn the smaller thumbscrews a few turns each
(Figure 15).Use a screwdriver in the slots, if necessary.
Now, try tightening or loosening one of the larger collimation
thumbscrews with your fingers (Figure 16). Look into the
focuser and see if the secondary mirror reflection has moved
closer to the center of the primary. You can tell this easily with
the collimation cap and mirror center mark by simply watching
to see if the “dot”of the collimation cap is moving closer or farther away from the ring on the center of the primary mirror.
Figure 13. To center the secondary mirror under the focuser,
hold the secondary mirror holder in place with one hand while
adjusting the center bolt with a Phillips screwdriver.Do not touch the
mirror’s surface!
Figure 14. Adjust the tilt of the secondary mirror by loosening or
tightening the three alignment set screws with a 2mm hex key.
Figure 15. The three small thumbscrews that lock the primary
mirror in place must first be loosened before any adjustments can
be made.
11
12
When you have the dot centered as much as possible in the
ring, your primary mirror is collimated. The view through the
collimation cap should resemble Figure 12e. Retighten the
locking thumbscrews.
A simple star test will tell you whether the optics are accurately
collimated.
Star-Testing the Telescope
When it is dark, point the telescope at a bright star and accurately center it in the eyepiece’s field of view. Slowly de-focus
the image with the focusing knob.If the telescope is correctly
collimated, the expanding disk should be a perfect circle
(Figure 17).If the image 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 donut. If the “hole” appears off-center, the telescope is out of collimation.
If you try the star test and the bright star you have selected is
not accurately centered in the eyepiece, the optics will always
appear out of collimation, even though they may be perfectly
aligned.It is critical to keep the star centered, so ov er time you
will need to make slight corrections to the telescope’s position
in order to account for the sky’s apparent motion.
Note About the Collimatable 2" Focuser (XT8)
The 2" focuser of the SkyQuest XT8 can be collimated using
three pairs of push-pull screws located at the base of the
focuser. The focuser was collimated at the factory however,
and should never need to be adjusted.Focuser collimation is
only required under very rare circumstances, but has been
made available for this telescope should such a need arise.
5. Astronomical Observing
For many users, the SkyQuest XT telescope will be a major
leap into the world of amateur astronomy. This section is
intended to get you ready for your first voyage through the
night sky.
Site Selection
Pick a location away from streetlights and bright yard lighting.
Avoid viewing over rooftops and chimneys, as they often have
warm air currents rising from them, which distort the image
seen in the eyepiece.
Similarly, you should not observe through an open window
from indoors.Better yet, choose a site out-of-town, away from
any “light pollution”.You’ll be stunned at how many more stars
you’ll see! Most impor tantly, make sure that any chosen site
has a clear view of a large portion of the sky.
Cooling the Telescope
All optical instruments need time to reach “thermal equilibrium” to achieve maximum stability of the lenses and mirrors,
which is essential for peak performance.When moved from a
warm indoor location to cooler air outside(or vice-versa), a telescope needs time to cool (or warm) to the outdoor
temperature. The bigger the instrument and the larger the
temperature change, the more time will be needed.
Allow at least 30 minutes for your SkyQuest XT to equilibrate.
If the scope experiences more than a 40° temperature change,
allow an hour or more.In the winter, storing the telescope outdoors in a shed or garage greatly reduces the amount of time
needed for the optics to stabilize.It also is a good idea to keep
the scope covered until the Sun sets so the tube does not heat
greatly above the temperature of the outside air.
The XT8 has the ability to mount a small fan to making cooling the tube faster. On the bottom of the mirror cell there are
four holes where a fan can be screwed on.
Seeing and Transparency
Atmospheric conditions play a huge part in quality of viewing.
In conditions of good “seeing,” star twinkling is minimal and
objects 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
Figure 16. The tilt of the primary mirror is adjusted by turning
one or more of the three larger thumbscrews.
Figure 17. 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.
Out of collimation Collimated
13
during the day has radiated off into space.Typically, seeing
conditions will be better at sites that have an altitude over
about 3000 feet. Altitude helps because it decreases the
amount of distortion-causing atmosphere you are looking
through.
A good way to judge if the seeing is good or not is to look at
bright stars about 40° abov e the horizon.If the stars appear to
“twinkle,” the atmosphere is significantly distorting the incom-
ing light, and views at high magnifications will not appear
sharp. If the stars appear steady and do not twinkle, seeing
conditions are probably good and higher magnifications will
be possible.Also, seeing conditions are typically poor during
the day. This is because the heat from the Sun warms the air
and causes turbulence.
Good “transparency” is especially important for observing
faint objects. It simply means the air is free of moisture,
smoke, and dust. All tend to scatter light, which reduces an
object’s brightness.
One good way to tell if conditions are good is by how many
stars you can see with your naked e ye .If you cannot see stars
of magnitude 3.5 or dimmer then conditions are poor.
Magnitude is a measure of how bright a star is, the brighter a
star is, the lower its magnitude will be.A good star to remember for this is Megrez (mag.3.4), which is the star in the Big
Dipper connecting the handle to the “dipper.” If you cannot see
Megrez, then you have fog, haze, clouds, smog, light pollution, or other conditions that are hindering your viewing. (See
Figure 18)
Let Your Eyes Dark-Adapt
Do not 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. Many observers
notice improvements after several hours of total darkness. As
your eyes become dark-adapted, more stars will glimmer into
view and you will be able to see fainter details in objects you
view in your telescope.So give yourself at least a little while to
get used to the dark before you begin observing.
To see what you are doing in the darkness, use a red light
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 is ideal, or you can cover the front of a
regular flashlight with red cellophane or paper. Beware, too,
that nearby porch and streetlights and automobile headlights
will spoil your night vision.
Tracking Celestial Objects
The Earth is constantly rotating about its polar axis, completing one full rotation every 24 hours; this is what defines a
“day.”We do not feel the Earth rotating, but we can tell that it
is at night by seeing the apparent movement of stars from
east to west.This movement translates into a rate of approximately .25° per minute , or 15 arc-seconds per second.(There
are 60 arc-minutes in 1°, and 60 arc-seconds in one arcminute.) This is called the sidereal rate.
When you observe any astronomical object, you are watching
a moving target.This means the telescope’s position must be
continuously updated over time to keep an object in the field
of view. This is easy to do with the SkyQuest XT because of
its smooth motions on both axes. As the object moves off
toward the edge of the field of view, you just lightly nudge the
telescope to bring it back to the center.
You will notice that it is more difficult to “track” objects when
the telescope tube is aimed nearly straight up.This is inherent
to the basic design of the Dobsonian, and stems from the fact
that there is very little mechanical leverage to mo ve in azim uth
when the tube is in a near vertical position.T o gain more le verage, try grasping the tube close to the altitude side bearings
with both hands.
Remember that objects appear to move across the field of
view faster at higher magnifications.This is because the field
of view becomes narrower.
Eyepiece Selection
By using eyepieces of varying focal lengths, it is possible to
attain many magnifications with the SkyQuest XT. The telescope comes with two high-quality Sirius Plössl eyepieces: a
25mm, which gives a magnification of 48x, and a 10mm,
which gives a magnification of 120x. Other eyepieces can be
used to achieve higher or low er po wers .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.At least to begin with, the two supplied eyepieces will
suffice nicely.
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!
Figure 18. Megrez connects the Big Dipper’s handle to it's “pan”.
It is a good guide to how conditions are. If you can not see Megrez
(a 3.4 mag star) then conditions are poor.
1.9
4.9
2.4
1.9
2.4
1.7
3.4
2.5
14
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 ma y
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.
Using 2" eyepieces (XT8 Only)
The SkyQuest XT8’s focuser is capable of accepting optional
2" eyepieces.To use 2" eyepieces you must remove the 1.25"
adapter from the focuser by turning the two thumbscrews that
hold it in place.Once this adapter is removed, insert a 2” eye-
piece directly into the eyepiece holder and use the same
thumbscrews to secure the larger eyepiece.
2" eyepieces are desirable because they provide a wider field
of view than 1.25" eyepiece. Many obser vers own at least one
2" eyepiece to yield the largest field of view possib le for looking
at wide deep-sky objects, such as open star clusters or
gaseous nebulae.You’ll be stunned at the large fields of view
that 2" eyepieces deliver.You’ll feel like you’re floating in space!
Now that you are all set up and ready to go, one critical
decision must be made: what to look at?
A. The Moon
With is rocky and cratered surface, the Moon is one of the
most interesting and easy subjects to view with your scope.
The best time to view it is during its partial phases when shadows fall on the craters and canyon walls to give them
definition.While the full moon may look like a tempting target,
it is not optimal for viewing! The light is too bright and surface
definition is low.
Even at partial phases the Moon is very bright. Use of an
optional Moon filter to helps to dim the glare.It simply threads
onto the bottom of the eyepiece. You’ll find the Moon filter
improves viewing comfort, and helps bring out the subtle features of the lunar surface.
B. The Sun
You can change your nighttime telescope into a daytime Sun
viewer by installing an optional full-aperture solar filter over
the front opening of the telescope. The primary attraction is
sunspots, which change shape, appearance, and location
daily. Sunspots are directly related to magnetic activity in the
Sun. Many observers like to make drawings of sunspots to
monitor how the Sun is changing from day to day.
Important Note: Do not look at the Sun with any optical
instrument without a professionally made solar filter, or
permanent eye damage could result. Also, be sure to
cover the finder scope, or better yet, remove it altogether.
C. The Planets
The planets don’t stay put like the stars, so to find them you
should refer to Sky Calendar at our website telescope.com, or
to charts published monthly in Astronomy, Sky & Telescope,
or other astronomy magazines. Venus, Mars, Jupiter, and
Saturn are the brightest objects in the sky after the Sun and
the Moon.Your SkyQuest XT is capable of showing you these
planets in some detail. Other planets may be visible but will
likely appear starlike. Because planets are quite small in
apparent size, optional higher power eyepieces are recommended and often needed for detailed observations. Not all
the planets are generally visible at any one time.
JUPITER The largest planet, Jupiter, is a great subject for
observation. You can see the disk of the giant planet and
watch the ever-changing positions of its four largest moon: Io,
Callisto, Europa, and Ganymede. Higher power eyepieces
should bring out the cloud bands on the planet’s disk and the
Great Red Spot.
SATURN The ringed planet is a breathtaking sight. 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 necessar y for a
good view. Look closely and you should see the Cassini division, a thin, dark gap in the rings.You should also see one or
more of Saturn’s moons, which look like f aint stars .The brightest is the 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 The Red Planet makes a close approach to Earth
every two years. Observing Mars is most favorable at these
times.You should see salmon-colored disk with some distinct
dark patches, and you may be able to spot a whitish polar ice
cap.To see surface detail on Mars, you will need a high power
eyepiece and very steady air!
D. The Stars
Stars will appear as tiny points of light. Even powerful telescopes cannot magnify stars to appear as anything more than
pinpoints.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 a star slightly can help bring out its color.
E. Deep-Sky Objects
Under dark skies, you can observe a wealth of fascinating
deep-sky objects; that is, objects that reside outside of our
solar system.These include gaseous nebulas, open and globular star clusters, and a variety of different types of galaxies.
The large apertures of SkyQuest XT Dobsonians are par ticularly well suited to gathering light, which is critical for
observing these usually faint celestial entities. For deep-sky
observing it is important that you find an obser ving site well
away from light pollution.Take plenty of time to let your eyes
adjust to the darkness.As you become more experienced and
your observing skills get sharper, you will be able to ferret out
more and more subtle details and structure from these fascinating objects.Do not expect to see color in deep-sky objects,
however, as human eyes are not sensitive to color from faint
light.
How to Find Deep-sky Objects: Starhopping
Starhopping, as it is called by astronomers, is perhaps the
simplest way to hunt down objects to view in the night sky. It
entails first pointing the telescope at a star close to the object
you wish to observe, and then progressing to other stars closer and closer to the object until it is in the field of view of the
eyepiece. It is a very intuitive technique that has been
employed for hundreds of years by professional and amateur
astronomers alike. Keep in mind, as with any new task, that
starhopping may seem challenging at first, but will become
easier over time and with practice.
To starhop, only a minimal amount of additional equipment is
necessary. A star chart or atlas that shows stars to at least
magnitude 5 is required. Select one that shows the positions
of many deep-sky objects, so you will have a lot of options to
choose from.If you do not know the positions of the constellations in the night sky, you will need to get a planisphere to
identify them.
Start by choosing bright objects to view.The brightness of an
object is measured by its visual magnitude; the brighter an
object, the lower its magnitude.Choose an object with a visual magnitude of 9 or lower. Many beginners start with the
Messier objects, which represent some of the best and brightest deep-sky objects, first catalogued about 200 years ago by
the French astronomer Charles Messier.
Determine in which constellation the object lies. Now, find the
constellation in the sky. If you do not recognize the constellation on sight, consult a planisphere.The planisphere gives an
all-sky view and shows which constellations are visible on a
given night at a given time.
Now look at your star chart and find the brightest star in the
constellation that is near the object that you are trying to find.
Using the finder scope, point the telescope at this star and
center it on the crosshairs Next, look again at the star chart
and find another suitably bright star near the bright star currently centered in the finder.Keep in mind that the field of view
of the finder scope is 7°, so you should choose a star that is
no more than 7° from the first star, if possible. Move the telescope slightly, until the telescope is centered on the new star.
Continue using stars as guideposts in this way until you are
the approximate position of the object you are trying to find
15
(Figure 19). Look in the telescope’s eyepiece, and the object
should be somewhere within the field of view.If it’s not, sw eep
the telescope carefully around the immediate vicinity until the
object is found.
If you have trouble finding the object, start the starhop again
from the brightest star near the object you wish to view.This
time, be sure the stars indicated on the star chart are in fact
the stars you are centering in the finder scope and telescope
eyepiece.Remember the telescope and the finder scope will
give you inverted images, keep this in mind when you are
starhopping from star to star.
Note About Astrophotography
SkyQuest Dobsonians are designed for visual, not photographic use.The Dobsonian mount is not an equatorial-type
mount, so it cannot be motor driven for long exposure
astrophotography. SkyQuests have also been optically optimized for visual use, since photographic optimization
degrades visual performance.
With that in mind, however, it is possible to do some simple
astrophotography with a SkyQuest. With the use of afocal
photography techniques (where the camera is simply placed
to the eyepiece to take a picture) and digital cameras, it is
possible to take pictures of bright objects.Certain photographic aids, such as the Orion SteadyPix, can help in taking
photos by the afocal method.
Figure 19. Starhopping is a good way to locate hard-to-find
objects. Refer to a star chart to map a route to the object that uses
bright stars as guideposts. Center the first star you’ve chosen in the
finder scope and telescope eyepiece (1).Now move the scope
carefully in the direction of the next bright star (2), until it is
centered. Repeat (3&4). The last hop (5) should place the desired
object in the eyepiece.
16
6. Care and Maintenance
If you give your telescope reasonab le care, it will last a lif etime.
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
caps on the front of the scope and on the focuser when it is not
in use. For maximum protection during storage, we recommend placing the telescope in a case to prevent any dust and
moisture from accumulating on exposed surfaces.
The telescope requires very little mechanical maintenance.
The optical tube is made of 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.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 finderscope. Never use regular glass cleaner or cleaning fluid
designed for eyeglasses
Before cleaning with fluid and tissue, 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 the telescope’s mirrors very
often; nor mally once every year or so. Covering the telescope
with the dust cover when it is not in use will help 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 secondar y mirror of
your telescope are front-surface aluminized and overcoated
with hard silicon dioxide, 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 secondar y mirror, it must be removed from the
telescope. Do this by holding the secondary mirror holder stationary with your fingers (don’t touch the mirror itself) while
unthreading the Phillips head screw in the center hub of the 4vaned spider. Completely unthread the screw from the holder,
and the holder will come loose in your fingers.Be careful not
to lose the spring on the Phillips head screw.
Handle the mirror and its holder carefully.You do not need to
remove the secondary mirror from its holder for cleaning.To
clean the secondary mirror, follow the procedure described
below for cleaning the primary mirror.
To clean the primar y mirror, carefully remove the mirror cell
from the telescope. To do this, you must remove the screws
that connect the entire mirror cell to the steel tube. These
screws are located on the outer edge of the mirror cell.
Now, remove the mirror from the mirror cell by removing the
three mirror clips that secure the mirror in its cell. Use a
Phillips head screwdriver to unthread the mirror clip anchor
screws. Next, hold the mirror by its edge, and remove it from
the mirror cell. Be careful not to touch the aluminized surface
of the mirror with your fingers.Set the mirror on a clean, soft
towel. Fill a clean sink, free of abrasive cleanser, with roomtemperature 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 is a very dirty mirror).
Wipe the mirror underwater 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 par ticles 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 b ulb”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 bottom and the edges 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.
17
7. Specifications
SkyQuest XT 6"
Primary mirror focal length: 1200mm
Primary mirror diameter:150mm
Focal Ratio:f/8.0
Focuser: Rack and pinion. Accepts 1.25" eyepieces
Eyepieces: 25mm & 10mm Sirius Plössl, fully coated with
multi-coatings, 1.25" barrel diameter
Magnification with supplied eyepieces:48x & 120x
Finder scope: 6x power, 30mm aperture, achromatic, 7° field
of view
Finder scope bracket: Dovetail base, spring-loaded X-Y
alignment
Eyepiece rack:Holds three 1.25" eyepieces
Mirror coatings: Aluminum with SiO
2
overcoat.
Minor axis of secondary mirror: 34.5mm
Weight:38 lbs., 6 oz.
Tube length: 45.5"
Tube outer diameter:7.25"
SkyQuest XT 8"
Primary mirror focal Length: 1200mm
Primary mirror diameter:203mm
Focal Ratio:f/5.9
Focuser: Rack and pinion. Accepts 2" eyepieces and 1.25"
eyepieces with adapter.
Eyepieces: 25mm & 10mm Sirius Plössl, fully coated with
multi-coatings, 1.25" barrel diameter
Magnification with supplied eyepieces:48x & 120x
Finder scope: 6x power, 30mm aperture, achromatic, 7° field
of view
Finder scope bracket: Dovetail base, spring-loaded X-Y
alignment
Eyepiece rack: Holds three 1.25" eyepieces and one 2" eye-
piece
Mirror coatings: Aluminum with SiO
2
overcoat.
Minor axis of secondary mirror: 47.0mm
Weight:42 lbs., 10 oz.
Tube length: 46.5"
Tube outer diameter:9.25"
18
One-Year Limited Warranty
This Orion SkyQuest XT telescope 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 W ay, 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, mishan-
dled, or modified, nor does it apply to normal wear and tear.This warranty gives you specific
legal rights, and you may also ha ve other rights, which vary from state to state.For further warranty service information, contact: Customer Service Department, Orion Telescopes &
Binoculars, P.O.Box 1815, Santa Cruz, CA 95061; (800)676-1343.
Orion Telescopes & Binoculars
Post Office Box 1815, Santa Cruz, CA 95061
Customer Support Help Line (800)676-1343 • Day or Evening
Loading...