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IN 096 Rev. A 0898
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
INSTRUCTION MANUAL
Orion
®
Observer
™
70mm EQ
#9802 Equatorial Refracting Telescope
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Tube rings
Tube ring clamps
Finder scope
Finder scope bracket
Finder scope alignment
screws (3)
Focuser drawtube
Eyepiece
Star diagonal
Focus knob
Declination slow-motion control
Declination lock knob
Latitude lock knob (hidden)
Latitude scale
Right ascension setting circle
Right ascension
slow-motion control
Tripod leg
Leg lock thumbscrew
Objective lens
Dew shield
Tube ring mounting bolt
Declination setting circle
Right ascension lock knob (hidden)
Counterweight shaft
Counterweight
Counterweight lock knob
Retaining washer and screw
Azimuth lock knob (hidden)
Tripod leg attachment bolt
Accessary tray bracket
Accessory tray
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Figure 1. Observer 70 EQ Parts Diagram
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C
ongratulations on your purchase of a quality Orion telescope.
Your new Observer 70 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 and 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.......................................................................................................4
4. Aligning the Finder Scope .................................................................................................... 5
5. Setting Up and Using the Equatorial Mount......................................................................... 5
6. Using the Telescope—Astronomical Viewing ....................................................................... 6
7. Terrestrial Viewing ................................................................................................................ 9
8. Care and Maintenance......................................................................................................... 9
9. Specifications........................................................................................................................ 9
10. Suggested Accessories ........................................................................................................9
1. Parts List
Qty. Description
1 Optical tube assembly
1 German-type equatorial mount
2 Slow-motion control cables
1 5x crosshair finder scope
1 Finder scope bracket
1 Counterweight
1 Counterweight shaft
1 25mm (36x) Kellner eyepiece (1.25")
1 90° mirror star diagonal
1 Tripod accessory tray
3 Tripod legs
3 Accessory tray screws with wing nuts and washers
1 Objective lens 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 during the warranty period,
you must use the original packaging.
Assembling the telescope should take only about 15 minutes.
Be careful not to overtighten screws and bolts or the threads
may strip.
During assembly (and anytime, for that matter), DO NOT
touch any of the lenses of the telescope, finder scope, or eyepieces, or the mirror of the diagonal, with your fingers. The
optical surfaces have delicate coatings on them that can 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 bolt into the hole in the mount and lightly tightening the
wing nut finger-tight. (Use the screwdriver tool provided
on the head of the bolt while tightening the wing nut.) Note
that the hinged accessory tray bracket on each leg should
face inward.
2. Thread the three thumbscrews into the lower leg joints.
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 equatorial mount attached, stand the tripod upright
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 and washers provided. Do not tighten the wing nuts yet.
4. Now, with the accessory tray attached but not tightened,
spread the tripod legs apart as far as they will go, until the
accessory tray brackets are taut. Then tighten the wing
nuts of the accessory tray screws.
5. Next, tighten the wing nuts of the tripod leg bolts at the
base of the equatorial mount.
6. Orient the equatorial mount as it appears in Figure 1, with
the latitude scale set at about a 40° angle. Tighten the latitude adjustment knob, the declination (Dec.) and right
ascension (R.A.) lock knobs, and the azimuth lock knob all
finger-tight.
7. Slide the counterweight on to the counterweight shaft.
Make sure that the screw that holds the retaining washer
at the bottom end of the shaft is tightened. This washer
will prevent the counterweight from slipping off the shaft
and possibly onto your foot if the counterweight lock knob
should come loose! Now, with the counterweight lock
knob loose, hold the counterweight in one hand and the
thread the shaft into the equatorial mount (base of declination axis) with the other hand. When it is threaded all
the way in, position the counterweight about halfway up
the shaft and tighten the counterweight lock knob.
8. Remove the tube rings from the telescope tube. Attach the
ring to the equatorial head with the two hex-head bolts
provided. Then lay the telescope tube in the (open) tube
rings, with the rings about midway along the tube’s length,
as in Figure 1. (Note that the Dec. slow-motion shaft,
where the Dec. slow-motion control cable attaches,
should be pointing back toward the eyepiece end of the
telescope. If it isn’t, remove the telescope optical tube,
loosen the Dec. lock knob, and rotate the equatorial head
180° on the Dec. axis.) Now close the tube rings over the
optical tube and tighten the tube ring clamps finger-tight to
secure the telescope.
9. Now attach the two slow-motion cables to the R.A. and
Dec. slow-motion shafts of the equatorial mount by positioning the setscrew on the end of the cable over the
indented slot on the shaft, then tightening the setscrew.
10.Attach the finder scope bracket to the optical tube over the
two pre-installed bolts located near the focuser. It doesn’t
matter whether the slanted bracket stem slants forward or
backward; choose whichever orientation you like. Secure
the bracket in place with the two round thumbscrews. Do
not loosen the two small hex nuts at the base of the bolts,
as they keep them from falling into the optical tube.
11.Install the finder scope in the bracket. To do this, first
unscrew the three alignment screws a few turns so they
don’t hinder insertion of the finder scope. The larger,
objective lens of the finder scope should face the same
direction as the objective lens of the main telescope. Then
lightly tighten the three alignment screws until the finder
scope is held securely.
12.Insert the chrome barrel of the star diagonal into the
focuser drawtube and secure with the thumbscrew on the
focuser drawtube.
13.Then insert the 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.)
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 on the
R.A. axis, then on the Dec. axis.
1. Keeping one hand on the telescope optical tube, loosen
the R.A. lock knob. 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.
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4. To balance the telescope on the Dec. axis, first tighten the
R.A. lock knob, with the counterweight shaft still in the
horizontal position.
5. With one hand on the telescope optical tube, loosen the
Dec. lock knob. The telescope should now be able to
rotate freely about the Dec. axis. Loosen the tube ring
clamps two or three turns, until you can slide the telescope tube forward and back inside the rings (this can be
aided by using a slight back-and-forth twisting motion on
the optical tube while you push or pull on it).
6. Position the telescope so that it remains horizontal when you
carefully let go with both hands. This is the balance point.
7. Retighten the tube ring clamps.
The telescope is now balanced on both axes. Now when you
loosen the lock knobs on the axes and manually point the telescope, it should move without resistance and 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 that they
point to exactly the same spot in the sky.
Alignment is easiest to do in daylight hours. First, insert your
lowest-power eyepiece (longest focal length, if you have
more than one) into the star diagonal. Then loosen the R.A.
and Dec. lock knobs 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 quarter-mile
away. Move the telescope so the target object appears in the
very center of the field of view when you look into the eyepiece.
Now tighten the R.A. and Dec. lock knobs. Use the slowmotion controls to recenter the object in the field of view, if it
moved off center when you tightened the lock knobs.
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. By
loosening one alignment screw and tightening another, you
change the line of sight 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.
Check the alignment by pointing the main telescope at another object and centering it in the finder scope. Then look
through the main telescope eyepiece and see if the object is
centered. If it is, your job is done. If it isn’t, make the neces-
sary adjustments to the finder scope’s alignment screws until
the object is centered in both instruments.
The finder scope can be focused by rotating the knurled ring
of its eyepiece. 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 have no doubt 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 is designed to compensate for that motion, allowing you to easily keep
astronomical objects from drifting out of the telescope’s field
of view when you’re observing them.
The equatorial mount enables you to follow, or track, objects
by slowly rotating the telescope on its right ascension axis,
using only the R.A. slow-motion cable. But first the mount
must be aligned with the Earth’s rotational axis.
For Northern Hemisphere observers, this is achieved by simply 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 2). 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). Consult a star
atlas or other reference book for instructions on polar-aligning your telescope in the Southern Hemisphere.
Polar Alignment
For general visual observation, an approximate polar alignment
is sufficient. This must be done at night, when Polaris is visible.
1. Level the equatorial mount by adjusting the length of the
three tripod legs accordingly.
2. Loosen the latitude lock knob and tilt the mount until the
pointer on the latitude scale is set at the latitude of your
observing site. For example, if your latitude is 40° North,
set the pointer to 40. Then retighten the latitude lock knob.
If you don’t know your latitude, consult a geographical
atlas to find it.
The latitude setting should not have to be adjusted again
unless you move to a different viewing location some distance away.
3. Loosen the Dec. lock knob 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 knob.
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4. Next, loosen the azimuth lock knob at the base of the
equatorial mount. Rotate the entire equatorial mount in
the horizontal direction until the R.A. axis points roughly at
Polaris. Retighten the lock knob.
The equatorial mount is now polar-aligned for casual observing.
More precise polar alignment is required for astrophotography.
Several methods exist and are described in many amateur
astronomy reference books and astronomy magazines.
Note that from this point on in your observing session, you
should not make any further adjustments in the azimuth or
the latitude of the mount, nor should you move the tripod.
Doing so will negate the polar alignment. The telescope
should only be moved about its R.A. and Dec. axes.
Tracking Celestial Objects
When you observe a celestial object through the telescope,
you’ll see it drift slowly across the field of view. To keep it in
the field, if your equatorial mount is polar-aligned, just turn the
R.A. slow-motion control. The Dec. slow-motion control is not
needed for tracking. Objects will appear to move faster at
higher magnifications, because the field of view is narrower.
Understanding the Setting Circles
The setting circles on an equatorial mount enable you to
locate celestial objects by their “celestial coordinates.” Every
object resides in a specific location on the “celestial sphere,”
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
upper set of numbers (farthest from the R.A. gear) apply to
viewing in the Northern Hemisphere, while the numbers
below them apply to viewing in the Southern Hemisphere.
The Dec. setting circle is scaled in degrees (there are 60 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 (5 degrees south of the celestial equator) and 27
minutes in declination.
Before you can use the setting circles to locate objects, they
must first be calibrated. The declination setting circle was calibrated at the factory, and should read 90° when the
telescope optical tube is pointing exactly along the polar axis.
If it does not read 90°, it may have to be reset.
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 knobs on the equatorial
mount (not the azimuth lock knob or latitude adjustment
knob), so the telescope optical tube can move freely.
3. Point the telescope at the bright star near the celestial
equator whose coordinates you know. Center the star in
the telescope’s field of view. Lock the R.A. and Dec. lock
knobs.
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 knob and rotate the telescope until
the Dec. value from the star atlas matches the reading on
the Dec. setting circle. Retighten the lock knob.
2. Loosen the R.A. lock knob and rotate the telescope until
the R.A. value from the star atlas matches the reading on
the R.A. setting circle. Retighten the lock knob.
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.
6. Using the 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 street lights, 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, which 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.
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Aiming the Telescope
To view an object in the main telescope, first loosen both the
R.A. and Dec. lock knobs. Aim the telescope at the object you
wish to observe by “eyeballing” along the length of the telescope tube (or use the setting circles to “dial in” the object’s
coordinates). Then look through the (aligned) finder scope and
move the telescope tube until the object is centered on the
crosshairs. Retighten the R.A. and Dec. lock bolts. Then center the object on the finder’s crosshairs using the R.A. and Dec.
slow-motion controls. The object should now be visible in the
main telescope with a low-power (long focal length) eyepiece.
Focusing the Telescope
Practice focusing the telescope in the daytime before using it
for the first time at night. Start by positioning the focuser near
the center of its adjustment range. Make sure the knurled
focus lock knob on the top of the focuser housing is loosened,
to allow the drawtube to move freely. Insert an eyepiece into
the focuser and secure with the thumbscrew. Point the telescope at a distant subject and get it in the field of view. Now,
slowly rotate one of the focusing knobs until the object comes
into sharp focus. Go a little bit beyond sharp focus until the
image just starts to blur again, then reverse the rotation of the
knob, just to make sure you hit the exact focus point. The telescope can only focus on objects at least 50 to 100 feet away.
It will not focus without the star diagonal in place.
As with all refractor telescopes used with a standard 90° star
diagonal, the image you see will be right-side up, but
reversed left-to-right. (Correct-image diagonals are available, and may be purchased separately, though the image
quality is slightly reduced.)
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 (power)
For example, the Observer 70 EQ, which has a focal length
of 700mm, used in combination with a 25mm eyepiece, yields
a power of
700 ÷ 25 = 28x.
Every telescope has a useful limit of power of about 45x–60x per
inch of aperture (diameter of objective lens). 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’ve located and
looked at the object with it, you can try switching to a higherpower eyepiece to ferret out more detail, if atmospheric
conditions permit. If the image you see is not crisp and
steady, reduce the magnification by switching to a longerfocal-length eyepiece. As a general rule, a small but
well-resolved image will show more detail and provide a more
enjoyable view than a dim and fuzzy, overmagnified image.
Camera Attachment
A 35mm single-lens reflex (SLR) camera body can easily be
attached to the Observer 70mm enabling you to take pictures
through the telescope. All that is needed is one additional
part, called a T-ring, which is specific to your model of camera (see the Orion catalog for selection).
Remove the eyepiece and diagonal from the telescope optical tube. Also remove any lenses that may already be
attached to your camera body. Now, connect the T-ring to
your camera. The T-ring, with your camera attached, threads
directly onto the end of the telescope. When used in this configuration, the Observer 70 acts as a 700mm telephoto lens
(the focal length of the telescope).
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. Many observers
notice improvements after several hours of total darkness. As
your eyes become dark-adapted, more stars will glimmer into
view and you’ll be able to see fainter details in objects you
view in your telescope. Exposing your eyes to very bright
daylight for extended periods of time can adversely affect
your night vision for days. So give yourself at least a little
while to get used to the dark before you begin observing.
To see what you’re doing in the darkness, use a red-filtered
flashlight rather than a white light. Red light does not spoil
your eyes’ dark adaptation like white light does. A flashlight
with a red LED light 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.
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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. Asimple planisphere,
or star wheel, can be a valuable tool both for learning the constellations and for determining which ones are visible on a
given night at a given time.
A good star chart or atlas will come in very handy for helping
find objects among the dizzying multitude of stars overhead.
Except for the Moon and the brighter planets, it’s pretty timeconsuming and frustrating to hunt for objects randomly,
without knowing where to look. You should have specific targets in mind before you begin observing.
Start with a basic star atlas, one that shows stars no fainter
than 5th or 6th magnitude. In addition to stars, the atlas will
show the positions of a number of interesting deep-sky
objects, with different symbols representing the different
types of objects, such as galaxies, open star clusters, globular clusters, diffuse nebulas, and planetary nebulas. So, for
example, your atlas might show that there is a globular cluster sitting just above the lid of the “Teapot” pattern of stars in
Sagittarius. You then know to point your telescope in that
direction to home in on the cluster, which happens to be 6.9magnitude Messier 28 (M28).
You can see a great number and variety of astronomical
objects with your Observer 70 EQ, including:
The Moon
With its rocky, cratered surface, the Moon is one of the easiest and most interesting targets to view with your telescope.
The best time to observe our one and only natural satellite is
during a partial phase, that is, when the Moon is NOT full.
During partial phases, shadows on the surface reveal more
detail, especially right along the border between the dark
and light portions of the disk (called the “terminator”). A full
Moon is too bright and devoid of surface shadows to yield a
pleasing view.
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 atmospheric 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 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 Y ou probably won’t be able to see much surface detail
on the Red Planet, but if conditions are particularly good you
may notice some light and dark areas, and possibly even a
white polar ice cap.
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.
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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, T urn Left at Orion
, and
The Universe From Your Backyard.
7. Terrestrial Viewing
The Observer 70 EQ 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, nonreversed
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.
8. Care and Maintenance
If you give your telescope reasonable care, it will last a lifetime. Store it in a clean, dry, dust-free place, safe from rapid
changes in temperature and humidity. Do not store the telescope outdoors, although storage in a garage or shed is OK.
Small components like eyepieces and other accessories
should be kept in a protective box or storage case. Keep the
objective lens cap on the front of the telescope when it is not
in use.
Your Observer 70 EQ 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. Don’t use household cleaners or eyeglass-
type 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 may 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!
9. Specifications
Objective lens: 70mm-diameter (2.8") achromat
Objective lens coatings: multi-coated
Focal length: 700mm
Focal ratio: f/10
Eyepieces: 25mm Kellner, fully coated, 1.25"
Magnification: 28x (with 25mm eyepiece)
Finder scope: 5x magnification
Diagonal: 90° star diagonal, mirror type
Mount: German-type equatorial
Tripod: aluminum, adjustable
10. Suggested Accessories
Soft Carrying & Storage Bag (#15157)
Made of rugged nylon, this case holds everything: the tube assembly, the mount, and the tripod. Zipper access. Strap handles.
Explorer™ II Eyepieces
Every observer should have several eyepieces of different
focal lengths to allow viewing of astronomical subjects at different magnifications. These eyepieces feature 3- or
4-element lens designs, with a 50° apparent field of view.
Fully antireflection coated. Threaded for filters. 1.25" barrels.
6mm (#8153), 10mm (#8152), 13mm (#8151), 17mm (#8154)
Moon Filter (#5662)
Cuts lunar glare 87%, revealing much more surface detail.
Threads into barrel of 1.25" eyepieces.
Solar Filter (#7706)
Allows safe viewing of the Sun. See the march of sunspots
across the Sun’s surface. This full-aperture glass filter provides a pleasing yellow-orange image of our nearest star,
unlike Mylar filters, which produce a blue image.
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To find Polaris in the night sky, look north and find the Big Dipper. Extend an imaginary line from the two “Pointer Stars” in
the bowl of the Big Dipper. Go about five times the distance between those stars and you’ll reach Polaris, which lies within
1° of the north celestial pole (NCP).
Figure 2
Big Dipper
(in Ursa Major)
Little Dipper
(in Ursa Minor)
N.C.P.
Pointer Stars
Polaris
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One-Year Limited Warranty
This Orion Observer 70mm EQ Equatorial 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; (800) 676-1343.
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Orion Telescopes & Binoculars
Post Office Box 1815, Santa Cruz, CA 95061
Customer Support Help Line (800) 676-1343 • Day or Evening
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