Orion SkyView Deluxe 90mm 9401 Instruction Manual

INSTRUCTION MANUAL

Orion®

SkyView

#9401 Equatorial Refracting Telescope

™

Deluxe 90mm

Providing Exceptional Consumer Optical Products Since 1975

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

Corporate Offices [phone]

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

IN 093 Rev. A 0998

Objective lens

Dew shield

Tube ring mounting bolt

Declination setting circle

Declination lock lever (not pictured)

Latitude lock lever (not pictured)

Counterweight shaft

Counterweight

Counterweight lock knob

Retaining washer and knob

Azimuth adjustment knob

Tripod leg attachment bolt

Accessory tray

Accessary tray bracket

Tube rings

Tube ring clamps

Finder scope

Finder scope

bracket

Finder scope

alignment screws (6)

Eyepiece

Star diagonal

Focus knob

Declination slow-motion control

Right ascension lock lever

Polar axis finder scope

Right ascension

slow-motion control

Right ascension

setting circle

Latitude adjustment knob

Latitude scale

Tripod leg

Leg lock bolt

Rubber foot

Figure 1. SkyView Deluxe 90mm Parts Diagram

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Congratulations on your purchase of a quality Orion telescope. Your new SkyView Deluxe 90mm EQ

Refractor is designed for high-resolution viewing of astronomical objects. With its precision optics and
equatorial mount, you’ll be able to locate and enjoy hundreds of fascinating celestial denizens, including
the planets, Moon, and a variety of deep-sky galaxies, nebulas, and star clusters.

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; a star wheel, or planisphere, available from Orion or from your local telescope shop, will
greatly help. With a little practice, a little patience, and a reasonably dark sky away from city lights, you’ll
find your telescope to be a never-ending source of wonder, exploration, and relaxation.

These instructions will help you set up, properly use and care for your telescope. Please read them over
thoroughly before getting started.

Table of Contents

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

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

3. Balancing the Telescope ....................................................................................................... 5

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

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

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

7. Terrestrial Viewing ................................................................................................................. 9

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

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

1. Parts List

Qty. Description

1 Optical tube assembly

1 German-type equatorial mount

1 Polar axis finder scope

2 Slow-motion control cables

1 Counterweight

1 Counterweight shaft

2 Optical tube mounting rings

1 6x30 crosshair finder scope

1 Finder scope bracket

1 Mirror star diagonal (1.25")

1 25mm (40x) Plössl eyepiece (1.25")

1 9mm (111x) Plössl eyepiece (1.25")

1 Moon filter

3 Tripod legs

1 Tripod accessory tray with hardware

1 Objective lens dust cap

WARNING: Never look directly at the

Sun through your telescope or its finder
scope—even for an instant—without
a professionally made solar filter that
completely covers the front of the
instrument, or permanent eye damage could
result. Be sure to also cover
the front of the finder scope with aluminum
foil or another opaque material to prevent
physical damage to the internal
components of the scope itself as well as to
your eye. Young children should use this
telescope only with adult supervision.

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2. Assembly

Carefully open all of the boxes in the shipping container. Make
sure all the parts listed in Section 1 are present. Save the boxes
and packaging material. In the unlikely event that you need to
return the telescope, you must use the original packaging.

Assembling the telescope for the first time should take about
20 minutes. No tools are needed. All bolts should be tightened
securely to eliminate flexing and wobbling, but only tighten
them “finger tight.” Be careful not to over-tighten or the threads
may strip. Refer to Figure 1 during the assembly process.

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

1. Lay the equatorial mount on its side. Attach the tripod legs
one at a time to the base of the mount by sliding the tripod
leg attachment bolt into the slot in the mount and lightly
tightening the knob finger-tight. Note that the hinged
accessory tray bracket on each leg should face inward.

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

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

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

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

6. Remove the retaining knob and washers from the bottom
end of the counterweight shaft. Slide the counterweight
onto the shaft, then replace the washers and the retaining
knob. The washers and knob will prevent the counter­weight from slipping off the shaft and possibly onto your
foot if the counterweight lock knob should come loose!

7. At the top end of the counterweight shaft, note the knurled
shaft collar. Rotate it so as much of the threaded end of the
shaft as possible is visible. Now, with the counterweight
lock knob loose, grip the counterweight with one hand and
thread the shaft into the equatorial mount (at the base of
the declination axis) with the other hand. When it is thread­ed as far in as it will go, twist the shaft collar clockwise to
secure the shaft. Position the counterweight about halfway
up the shaft and tighten the counterweight lock knob.

8. Orient the equatorial mount as it appears in Figure 1, at a
latitude of about 40°, i.e., so the pointer next to the gold­colored latitude scale is pointing to the hash mark at “40.”
To do this, loosen the latitude lock lever (on the side of the
mount opposite the gold latitude scale), and turn the lati­tude adjustment knob until the pointer and the “40” line up.
Then tighten the latitude lock lever. Also tighten the decli­nation (Dec.) and right ascension (R.A.) lock levers.

9. Remove the caps from the narrow end of the polar scope
and the polar scope port in the equatorial mount. Insert
the narrow end of the polar scope into the open port. While
gripping the wide end of the polar scope (but not the eye­piece at the very end), thread it clockwise into the port
until it is secure.

10. Attach the two tube rings to the equatorial head, using the
captive tube ring bolts preinstalled in the equatorial head.
Open the tube rings.

11. Lay the telescope optical tube in the tube rings at about
the midpoint of the tube’s length. Rotate the tube in the
rings so the focus knobs are on the underside of the tele­scope. Close the rings over the tube and tighten the
knurled ring clamps finger-tight to secure the telescope in
position.

12. Now attach the two slow-motion cables to the R.A. and
Dec. worm gear shafts of the equatorial mount by position­ing the setscrew on the end of the cable over the indented
slot on the worm gear shaft, then tightening the setscrew.
The cables can be attached to either end of the shafts,
which ever is most convenient for you. But we recommend
that the Dec. cable extend toward the back end of the
telescope (as in the picture), since that’s where you’ll be
standing.

13. To install the finder scope bracket on the optical tube (adja­cent to the focus knobs), first remove the two knurled
mounting screws from the optical tube. Position the finder
scope bracket over the two holes in the telescope tube.
The bracket should be oriented so that the rings extend
toward the front of the telescope tube. Replace the knurled
mounting screws and tighten finger-tight.

14. Place the finder scope in the finder bracket by first backing
off all six alignment screws until the screw tips are flush
with the inside diameter of the finder bracket. Slide the
finder scope through the finder bracket rings with the
larger (objective) end pointing in the same direction as the
open end of the main telescope. Line up the groove on the
eyepiece end of the finder scope with the rear ring of the
finder bracket. Tighten the six alignment screws equally to
secure the finder scope in place.

15. Insert the chrome barrel of the star diagonal into the focuser
drawtube and secure with the thumbscrew on the drawtube.

16. Then insert an eyepiece into the star diagonal and secure
it in place with the thumbscrew on the diagonal. (Always
loosen the thumbscrews before rotating or removing the
diagonal or an eyepiece.)

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3. Balancing the Telescope

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

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

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

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 lever, with the counterweight shaft still in the
horizontal position.

5. With one hand on the telescope optical tube, loosen the
Dec. lock lever. 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).

6. Position the telescope in the mounting rings so it remains
horizontal when you carefully let go with both hands. This
is the balance point for the optical tube with respect to the
Dec. axis.

7. Retighten the tube ring clamps.

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

4. Aligning the Finder Scope

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

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

Point the main telescope at a discrete object such as the top
of a telephone pole or a street sign that is at least a quarter­mile away. Move the telescope so the target object appears in
the very center of the field of view when you look into the
eyepiece. Now tighten the R.A. and Dec. lock levers. Use the
slow-motion control knobs to re-center the object in the field of
view, if it moved off center when you tightened the lock levers.

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

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

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

5. Setting Up and Using
the Equatorial Mount

When you look at the night sky, you no doubt have noticed 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, page 11) is designed to
compensate for that motion, allowing you to easily “track” the
movement of astronomical objects, thereby keeping them from
drifting out of the telescope’s field of view while you’re observing.

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

Polar Alignment

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

To find Polaris in the sky, look north and locate the pattern of
the Big Dipper (Figure 3, page 11). The two stars at the end
of the “bowl” of the Big Dipper point right to Polaris.

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

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

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

2. Loosen the latitude lock lever. Turn the latitude adjustment
knob and tilt the mount until the pointer on the latitude
scale is set at the latitude of your observing site. If you
don’t know your latitude, consult a geographical atlas to
find it. For example, if your latitude is 35° North, set the
pointer to +35. Then retighten the latitude lock lever. The

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latitude setting should not have to be adjusted again
unless you move to a different viewing location some dis­tance away.

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

4. Lift and rotate the tripod so the telescope tube (and R.A.
axis) points roughly at Polaris. If you cannot see Polaris
directly from your observing site, consult a compass and
rotate the tripod so the telescope points North.

The equatorial mount is now approximately polar-aligned for
casual observing. More precise polar alignment is required for
astrophotography.

Polar Aligning Using the Polar Axis Finder

One of the unique features of your new SkyView Deluxe
mount is the polar axis finder scope. It fits conveniently inside
the equatorial mount, and contains a tiny star map that makes
precise polar alignment quick and easy. To use the polar axis
finder scope, follow these instructions:

1. Approximately polar-align the mount as outlined in the
procedure above.

2. Remove the caps that cover the polar finder (one on the
polar finder’s eyepiece and one on the equatorial mount).
Focus the polar finder by rotating its eyepiece. Now, sight
Polaris in the polar axis finder scope. If you have followed
the approximate polar alignment procedure accurately,
Polaris will probably be within the field of view. If it is not,
move the tripod left-to-right, and adjust the latitude up­and-down until Polaris is somewhere within the field of
view of the polar axis finder scope.

3. Shine a red flashlight down the front end of the polar finder
to illuminate the reticle within the field of view. Make sure
the flashlight shines in at an angle, so as not to block the
polar finder’s field of view. It may be helpful to have a friend
hold the flashlight while you look through the polar finder.
Note the constellations Cassiopeia and Ursa Major (the Big
Dipper) in the reticle (ignore the constellation Octans, as
this is provided for Southern Hemisphere observers). They
do not appear to scale, but they indicate the general posi­tions of Cassiopeia and Ursa Major relative to Polaris and
the north celestial pole (which is indicated by the cross at
the center of the reticle). Next, the reticle must be rotated so
the constellations depicted match their current orientation
in the sky when viewed with the naked eye. To do this,
release the R.A. lock lever and rotate the main telescope
about the R.A. axis until the reticle is oriented with the sky.
You may need to reposition the telescope about the declina­tion axis so the telescope does not bump the mount. Once
the reticle is correctly oriented, use the R.A. lock lever to
secure the main telescope’s position.

4. Now, use the azimuth and latitude adjustment knobs on
the mount to position the star Polaris inside the tiny circle
marked “Polaris” in the polar finder’s reticle. You must first
release the latitude lock lever and loosen the bolt that con-

nects the equatorial head to the tripod (underneath the
equatorial mount). Once Polaris is properly positioned
within the reticle, lock the latitude lock lever and retighten
the bolt that connects the equatorial head to the tripod.
You are now precisely polar-aligned.

If you do not have a clear view of Polaris from your observing
site, then you will not be able to use the polar axis finder
scope to precisely polar-align the telescope.

Note: 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.

Tracking Celestial Objects

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

Optional Motor Drives for Automatic Tracking
and Astrophotography

An optional DC motor drive (Orion AccuTrack SVD, #7825)
can be mounted on the R.A. axis of the SkyView Deluxe
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.

Understanding the Setting Circles

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

The R.A. setting circle is scaled in hours, from 1 through 24,
with small hash marks in between representing 10-minute
increments (there are 60 minutes in 1 hour of R.A.). The Dec.
setting circle is scaled in degrees (there are 60 arc-minutes in
1 degree of declination).

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

R.A. 5h 35.4m Dec. –5° 27'

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

Before you can use the setting circles to locate objects, the
mount must be precisely polar aligned, and the setting circles
must be calibrated.

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Calibrating the Declination Setting Circle

1. Loosen the Dec. lock lever and position the telescope as
accurately as possible in declination so it is parallel to the
R.A. axis of the equatorial mount. Re-tighten the lock lever.

2. Rotate the Dec. setting circle until the pointer reads exactly 90°.

Calibrating the Right Ascension Setting Circle

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

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

3 Point the telescope at the bright star near the celestial

equator whose coordinates you know. This information can
be taken from any star chart. Center the star in the tele­scope’s field of view. Lock the R.A. and Dec. lock levers.

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

Finding Objects With the Setting Circles

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

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

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

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

Confused About Pointing the Telescope?

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

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

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

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

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

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

6. Using Your Telescope—
Astronomical Observing

Choosing an Observing Site

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

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

Cooling the Telescope

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

Aiming the Telescope

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

7

Focusing the Telescope

Practice focusing the telescope in the daytime before using it
for the first time at night. Start by turning the focus knob until
the focuser drawtube is near the center of its adjustment
range. Insert the star diagonal into the focuser drawtube and
an eyepiece into the star diagonal (secure with the thumb­screws). Point the telescope at a distant subject and center it
in the field of view. Now, slowly rotate the focus knob until the
object comes into sharp focus. Go a little bit beyond sharp
focus until the image just starts to blur again, then reverse the
rotation of the knob, just to make sure you hit the exact focus
point. The telescope can only focus on objects at least 50 to
100 feet away.

Do You Wear Eyeglasses?

If you wear eyeglasses, you may be able to keep them on
while you observe, if your eyepieces have enough “eye relief”
to allow you to see the whole field of view. You can try this by
looking through the eyepiece first with your glasses on and
then with them off, and see if the glasses restrict the view to
only a portion of the full field. If they do, you can easily
observe with your glasses off by just refocusing the telescope
the needed amount.

Calculating the Magnification

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

Telescope focal length ÷ Eyepiece focal length =

Magnification

For example, the SkyView Deluxe 90mm, which has a focal
length of 1000mm, used in combination with a 25mm eye­piece, yields a power of

1000 ÷ 25 = 40x.

Every telescope has a useful limit of power of about 45x–60x
per inch of aperture. Claims of higher power by some telescope
manufacturers are a misleading advertising gimmick and
should be dismissed. Keep in mind that at higher powers, an
image will always be dimmer and less sharp (this is a funda­mental law of optics). The steadiness of the air (the “seeing”)
will limit how much magnification an image can tolerate.

Always start viewing with your lowest-power (longest focal
length) eyepiece in the telescope. After you have located and
looked at the object with it, you can try switching to a higher
power eyepiece to ferret out more detail, if atmospheric condi­tions permit. If the image you see is not crisp and steady,
reduce the magnification by switching to a longer focal length
eyepiece. As a general rule, a small but well-resolved image
will show more detail and provide a more enjoyable view than
a dim and fuzzy, over-magnified image.

Let Your Eyes Dark-Adapt

Don’t expect to go from a lighted house into the darkness of the
outdoors at night and immediately see faint nebulas, galaxies,

and star clusters—or even very many stars, for that matter. Your
eyes take about 30 minutes to reach perhaps 80% of their full
dark-adapted sensitivity. As your eyes become dark-adapted,
more stars will glimmer into view and you’ll be able to see
fainter details in objects you view in your telescope.

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

“Seeing” and Transparency

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

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

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

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

How to Find Interesting Celestial Objects

To locate celestial objects with your telescope, you first need
to become reasonably familiar with the night sky. Unless you
know how to recognize the constellation Orion, for instance,
you won’t have much luck locating the Orion Nebula, unless,
or course, you look up its celestial coordinates and use the
telescope’s setting circles. Even then, it would be good to
know in advance whether that constellation will be above the
horizon at the time you plan to observe. A simple planisphere,
or star wheel, can be a valuable tool both for learning the
constellations and for determining which ones are visible on
a given night at a given time.

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

Start with a basic star atlas, one that shows stars no fainter
than 5th or 6th magnitude. In addition to stars, the atlas will

8

show the positions of a number of interesting deep-sky
objects, with different symbols representing the different
types of objects, such as galaxies, open star clusters, globu­lar clusters, diffuse nebulas, and planetary nebulas. So, for
example, your atlas might show a globular cluster sitting just
above the lid of the “Teapot” pattern of stars in Sagittarius. You
then know to point your telescope in that direction to home in
on the cluster, which happens to be 6.9-magnitude Messier
28 (M28).

You can see a great number and variety of astronomical
objects with your SkyView Deluxe 90mm, including:

The Moon

With its rocky, cratered surface, the Moon is one of the easiest
and most interesting targets to view with your telescope. The
best time to observe our one and only natural satellite is dur­ing a partial phase, that is, when the Moon is NOT full. During
partial phases, shadows on the surface reveal more detail,
especially right along the border between the dark and light
portions of the disk (called the “terminator”). A full Moon is too
bright and devoid of surface shadows to yield a pleasing view.
Use the included Moon filter to dim the Moon when it is very
bright. It simply threads onto the bottom of the eyepieces
(you must first remove the eyepiece from the star diagonal to
attach the Moon filter).

The Planets

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

JUPITER The largest planet, Jupiter, is a great subject to
observe. You can see the disk of the giant planet and watch
the ever-changing positions of its four largest moons, Io,
Callisto, Europa, and Ganymede. If atmospheric conditions
are good, you may be able to resolve thin cloud bands on the
planet’s disk.

SATURN The ringed planet is a breathtaking sight when it is
well positioned. The tilt angle of the rings varies over a period
of many years; sometimes they are seen edge-on, while at
other times they are broadside and look like giant “ears” on
each side of Saturn’s disk. A steady atmosphere (good see­ing) is necessary for a good view. You may probably see a tiny,
bright “star” close by; that’s Saturn’s brightest moon, Titan.

VENUS At its brightest, Venus is the most luminous object in the
sky, excluding the Sun and the Moon. It is so bright that some­times it is visible to the naked eye during full daylight! Ironically,
Venus appears as a thin crescent, not a full disk, when at its peak
brightness. Because it is so close to the Sun, it never wanders too
far from the morning or evening horizon. No surface markings can
be seen on Venus, which is always shrouded in dense clouds.

MARS If atmospheric conditions are good, you may be able
to see some subtle surface detail on the Red Planet, possibly
even the polar ice cap. Mars makes a close approach to Earth

every two years; during those approaches its disk is larger
and thus more favorable for viewing.

Stars

Stars will appear like twinkling points of light in the telescope.
Even powerful telescopes cannot magnify stars to appear as
more than points of light! You can, however, enjoy the different
colors of the stars and locate many pretty double and multiple
stars. The famous “Double-Double” in the constellation Lyra
and the gorgeous two-color double star Albireo in Cygnus are
favorites. Defocusing the image of a star slightly can help
bring out its color.

Deep-Sky Objects

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

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

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

7. Terrestrial Viewing

The SkyView Deluxe 90mm Refractor may also be used for
long-distance viewing over land. For this application we rec­ommend substitution of an Orion 45° Correct-Image Diagonal
(#8790) for the 90° star diagonal that comes standard with the
telescope. The correct-image diagonal will yield an upright,
non-reversed image and also provides a more comfortable
viewing angle, since the telescope will be aimed more hori­zontally for terrestrial subjects.

For terrestrial viewing, it’s best to stick with low powers of 50x
or less. At higher powers the image loses sharpness and clar­ity. That’s because when the scope is pointed near the
horizon, it is peering through the thickest and most turbulent
part of the Earth’s atmosphere.

Remember to aim well clear of the Sun, unless the front
of the telescope is fitted with a professionally made solar
filter and the finder scope is covered with foil or some
other completely opaque material.

9

8. Care and Maintenance

9. Specifications

If you give your telescope reasonable care, it will last a life­time. Store it in a clean, dry, dust-free place, safe from rapid
changes in temperature and humidity. Do not store the tele­scope outdoors, although storage in a garage or shed is OK.
Small components like eyepieces and other accessories
should be kept in a protective box or storage case. Keep the
cap on the front of the telescope when it is not in use.

Your SkyView Deluxe telescope requires very little mechani­cal maintenance. The optical tube is aluminum 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 the Optics

A small amount of dust or a few specks on the glass objective
(main) lens will not affect the performance of the telescope. If
dust builds up, however, simply blow it off with a blower bulb,
or lightly brush it off with a soft camel hair brush. Avoid touch­ing optical surfaces with your fingers, as skin oil may etch
optical coatings.

To remove fingerprints or smudges from a lens, use photo­graphic-type lens cleaning fluid and lint-free optical lens
cleaning tissue. Do not use household cleaners or eyeglass­type cleaning cloth or wipes, as they often contain undesirable
additives like silicone, which don’t work well on precision
optics. Place a few drops of fluid on the tissue (not directly on
the lens), wipe gently, then remove the fluid with a dry tissue
or two. Do not “polish” or rub hard when cleaning the lens, as
this will scratch it. The tissue may leave fibers on the lens, but
this is not a problem; they can be blown off with a blower bulb.

Never disassemble the telescope or eyepieces to
clean optical surfaces!

Optical tube: Seamless aluminum

Objective lens diameter: 90mm (3.5")

Objective lens glass: crown and flint, achromat

Objective lens coating: multi-coated

Focal length: 1000mm

Focal ratio: f/11

Eyepieces: 25mm and 9mm Kellner, fully coated, 1.25"

Magnification: 40x (with 25mm), 111x (with 9mm)

Focuser: Rack and pinion

Diagonal: 90° star diagonal, mirror type, 1.25"

Finder scope: 6x magnification, 30mm aperture, achromatic,
crosshairs

Mount: German-type equatorial

Tripod: Aluminum

Motor drives: Optional

10

Declination (Dec.)
setting circle

Polar axis finder scope
port (front), with cap

Azimuth adjustment
knob

DECLINATION AXIS

Figure 2

Right ascension (R.A.)

setting circle

Polar axis finder scope

RIGHT ASCENSION (POLAR) AXIS

Latitude scale

Latitude adjustment

knob

Little Dipper

(in Ursa Minor)

Big Dipper

(in Ursa Major)

Pointer Stars

N.C.P.

Polaris

Cassiopeia

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

Figure 3

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One-Year Limited Warranty

This Orion SkyView Deluxe 90mm EQ Refractor is warranted against defects in materials or workman­ship for a period of one year from the date of purchase. This warranty is for the
benefit of the original retail purchaser only. During this warranty period Orion Telescopes & Binoculars
will repair or replace, at Orion’s option, any warranted instrument that proves to be defective, provided it
is returned postage-paid to: Orion Warranty Repair, 89 Hangar Way, Watsonville, CA 95076. If the prod­uct is not registered, proof of purchase (such as a copy of the original invoice) is required.

This warranty does not apply if, in Orion’s judgment, the instrument has been abused, mishandled, or
modified, nor does it apply to normal wear and tear. This warranty gives you specific legal rights, and you
may also have other rights, which vary from state to state. For further warranty service information, con­tact: Customer Service Department, Orion Telescopes & Binoculars, P. O. Box 1815, Santa Cruz, CA
95061; [phone].

Orion Telescopes & Binoculars

Post Office Box 1815, Santa Cruz, CA 95061

Customer Support Help Line [phone] • Day or Evening