Orion Observer 80ST User manual

INSTRUCTION MANUAL
IN 582 05/17
Orion®Observer™80ST
Equatorial Refractor
#10273
Customer Support:
www.OrionTelescopes.com/contactus
Corporate Offices:
89 Hangar Way, Watsonville CA 95076 – USA
Copyright © 2017 Orion Telescopes & Binoculars
All Rights Reserved. No part of this product instruction or any of its contents may be reproduced, copied,
modied or adapted, without the prior written consent of Orion Telescopes & Binoculars.
Providing Exceptional Consumer Optical Products Since 1975
®

2
Congratulations on your purchase of an Orion telescope.Your new Observer 80ST Equatorial Refractor is
a terric starter instrument for exploring the exotic wonders of the night sky. Designed to be compact and
easy to use, it will provide many hours of enjoyment for the whole family.
If you have never owned a telescope before, we would like to welcome you to amateur astronomy. Take
some time to familiarize yourself with the night sky. Learn to recognize the patterns of stars in the major
constellations. With a little practice, a little patience, and a reasonably dark sky away from city lights, you’ll
nd your telescope to be a never-ending source of wonder, exploration, and relaxation.
These instructions will help you set up, properly use, and care for your telescope. Please read them over
thoroughly before getting started.
WARNING: Never look directly at the Sun through
your telescope—even for an instant—without a
professionally made solar lter that completely
covers the front of the instrument, or permanent eye
damage could result. Young children should use this
telescope only with adult supervision.
Table of Contents
1. Parts List .................................2
2. Assembly .................................4
3. Preparing the Telescope for Operation...........5
4. Understanding and Using the Equartorial Mount...7
5. Astronomical Observing.....................10
6. Worthwhile Optional Accessories .............12
7. Telescope Care and Maintenance .............13
8. Specications.............................13
1. Parts List
Part. Quantity
A – Tripod legs 3
B – Hex head tripod mounting bolts (3”) 3
C – Washers (5/8”) 3
D – Wing nuts 3
E – Leg lock thumbscrews 3
F – Accessory tray 1
G – Screws 3
H – Washers (3/8”) 3
I – Wing nuts (small) 3
J – Equatorial mount 1
K – Azimuth lock knob (and washer) 1
L – Latitude adjustment bolt 1
M – Counterweight shaft 1
N – Counterweight lock knob 1
O – Counterweight 1
P – Slow-motion cables 2
Q – Mounting platform 1
R – Telescope optical tube 1
S – Red dot nder scope 1
T – Dust cover 1
U – 25mm Kellner eyepiece 1
V- 10mm Kellner eyepiece 1
W – Star diagonal 1

3
Figure 1. The parts of the Observer 80ST EQ telescope .
QA
L
P
K
JIHGFMVSUWE
D
C
B
O
T
R
N

4
2. Assembly
1. Attach the three aluminum tripod legs (A) to the mounting
platform (Q) (Figure 3a) with the three hinged leg braces
facing inward.Three hex-head bolts (B) each about 3" long,
with 5/8” washers (C) and wing nuts (D), are provided for
this purpose. Note that the bolts should be inserted from
the side of the leg that has the hex-shaped hole, so that
the bolt head seats in the hex-shaped hole (Figure 3b).
The washer then the wing nut are placed on the opposite
side on the exposed end of the bolt.
2. Attach a leg lock thumbscrew (E) to each leg as shown
(Figure 4). Extend the sliding inner portion of the adjust-
able-height tripod leg to the desired length for all three
legs. Lock in place by tightening the leg lock thumbscrews.
Do not over-tighten the leg lock thumbscrews or you
may damage the collar they are attached to.
3. Now stand the tripod upright, spreading the legs evenly
apart so the accessory tray can be positioned to attach to
the three leg braces.
4. Attach the accessory tray (F) to the leg brace supports
(Figure 5) with the three short screws (G), small (3/8”)
washers (H), and small wing nuts (I) provided. Place a
washer on the screw. Then place the accessory tray on
top of one of the leg braces so that the mounting screw
passes through the hole at one of the corners of the
accessory tray, and through the slot in the leg brace. Then
place another small washer on the screw and thread on
and tighten the wing nut. Repeat this procedure until the
tray is attached to all three leg braces.
The tripod is now fully assembled (Figure 6).Next you will
install the equatorial mount onto the tripod.
5. Locate the equatorial (EQ) mount (J) and place its base
into the hole in the center of the mounting platform (Q)
(Figure 7a). Then secure it in place with the azimuth lock
knob and washer (K) (Figure 7b).
6. Thread the latitude adjustment bolt (L) into the threaded
socket (Figure 8) until it contacts metal inside the housing.
7. Next, thread the counterweight shaft (M) into the base of
the Declination axis of the mount (Figure 9).
8. Thread the counterweight lock knob (N) into the counter-
weight (O) a few turns.
9. To slide the counterweight onto the counterweight shaft,
rst remove the Philips screw and washer from the end
of the shaft. Make sure the counterweight lock knob (N) is
loosened enough so that the metal pin inside the counter-
weight is clear of the shaft hole. Slide the counterweight
about 2 inches from the bottom of the counterweight shaft
and secure it in place with the lock knob (Figure 10). Then
replace the washer and screw at the end of the counter-
weight shaft.
10. Attach the slow motion cables (P) to the gear shafts as
shown in Figure 11. The longer cable should be attached
to the declination gear shaft; the shorter cable to the right
ascension gear shaft. Orient the cable so that the thumb-
Figure 2. The Observer 80ST EQ telescope fully assembled, with
key parts identied.
Figure 3. a) Attach the three tripod legs to the mount platform,
b) making sure the bolt’s hex-shaped head seats in the hex-shaped
recess of the tripod leg.
Washer
Wingnut
L
AA
A
E
E
E
P (Dec)
U
W
R
S
K
Q
P(R.A.)
J
N
O
M
F
R.A. Axis
Dec. Axis

5
screw seats in the groove of the gear shaft, as shown in
Figure 12, then rmly tighten the thumbscrew. If there is
a small rubber ball on the end of the shaft, you will have
to remove it in order to attach the cable. Also note that,
depending on your preference, you can attach the cable to
either the left or right side of the right ascension gear shaft.
Now the mount is properly attached to the tripod and outtted
for use (Figure 13). Next, you’ll attach the telescope optical
tube to the mount.
11. Remove the wing nuts and washers from the optical tube
mounting bolts that are pre-installed on the underside
of the telescope optical tube (R). Then lay the telescope
optical tube assembly onto the saddle plate (Figure 14),
passing the mounting bolts through the holes in the saddle
plate. Then place a washer on each bolt and re-attach the
wing nuts until tight. Be sure the focuser portion of the
optical tube is on the same side of the saddle as the slow-
motion control cable in Declination, as in Figure 14.
12. To attach the red dot nder scope (S) to the optical tube,
orient the nder scope as shown in Figure 15 and slide
the bracket foot into the nder scope base until it clicks.
(To remove the nder scope, press the small tab at the
back of the base and slide the bracket out.)
13. Insert the star diagonal (W) into the focuser drawtube and
tighten the two thumbscrews on the drawtube collar (Figure
16). Then insert the 25mm eyepiece (U) into the diagonal
and secure it by lightly tightening the thumbscrew on the
diagonal.
The telescope is now completely assembled! Before it can be
effectively used, however, there are a couple of things to do to
prepare the telescope for operation.
3. Preparing the Telescope
for Operation
Aligning and Using the Red Dot Finder Scope
The included red dot nder scope (Figure 17) makes pointing
your telescope almost as easy as pointing your nger! It’s a non-
magnifying aiming device that superimposes a tiny LED red dot
on the sky, showing exactly where the telescope is pointed. It
permits easy object targeting prior to observation in the higher-
power main telescope.
Before you can use the red dot nder scope, you must remove
the small plastic tab sticking out from the battery compartment
(Figure 17). Doing so will allow the pre-installed 3V CR-2032
Figure 4. Thread a leg lock thumbscrew onto each tripod leg as
shown, being careful not to overtighten.
Figure 5. Attach the accessory tray to each of the tripod three
leg brace supports using the provided hardware.
Figure 6. The fully assembled tripod.
Wing nut
Accessory tray Screw head
Washer
Washer
Leg

6
button cell battery to make contact with the nder scope’s elec-
tronic circuitry to power the nder’s red LED illuminator. The tab
can then be discarded.
To use the red dot nder scope properly, it must be aligned with
the main telescope. This is easiest to do during daylight hours,
before observing at night. Follow this procedure:
1. First, remove the dust cap (T) from the front of the tele-
scope.
2. With the star diagonal and 25mm eyepiece already in
place from step 13 above, point the telescope at a well-
dened land target (e.g., the top of a telephone pole) that’s
at least a quarter mile away. Center the target in the eye-
piece by turning the slow-motion cables (P) as needed
to point the telescope. For larger telescope movement,
release the R.A. and Dec. axis lock knobs (Figure 18) and
move the telescope tube by hand to the approximate loca-
tion, then retighten the lock knobs and make ner pointing
adjustments with the slow motion cables.
Note: The image in the telescope will appear mirror reversed,
i.e., reversed left to right. This is normal for refractor tele-
scopes used for astronomical observing with a standard star
diagonal. (For terrestrial observing we recommend using an
optional“correct image” diagonal, which will serve up a cor-
rectly oriented view.)
3. Now that a distant target is centered in the main tele-
scope’s eyepiece, turn on the red dot nder scope by slid-
ing the power switch to ON (refer to Figure 17). The “1”
position provides dim illumination while the “2” position
provides brighter illumination. Typically the dimmer setting
is used under dark skies and the brighter setting is used
under light-polluted skies or in daylight. Position your eye
at a comfortable distance from the rear of the unit. Look
through the rear of the nder scope with both eyes open
to see the illuminated red dot. The target object should
appear in the eld of view somewhere near the red dot.
4. You’ll want to center the target object on the red dot. To do
so, without moving the telescope, use the nder scope’s
vertical and horizontal adjustment knobs (shown in Figure
17) to position the red dot on the object.
5. When the red dot is centered on the distant object, check
to make sure the object is still centered in the telescope’s
eyepiece. If it isn’t, re-center it then adjust the finder
scope’s alignment again. When the object is centered in
the telescope eyepiece and on the nder scope’s red dot,
the nder scope is properly aligned with the telescope.
The red dot nder scope’s alignment should be checked
before every observing session.
At the end of your observing session, be sure to slide the power
switch on the red dot nder scope to OFF to preserve battery life.
Balancing the Telescope
In order for the telescope to move smoothly on its mechanical
axes, it must rst be balanced as follows:
1. Loosen the R.A. lock knob half a turn or so (Figure 19).
With the R.A. lock knob loosened, the telescope mount
will turn freely about the polar (R.A.) axis. Rotate the tele-
scope about the polar axis so that the counterweight shaft
is parallel to the ground (horizontal), as shown.
Figure 7. a) Install the equatorial mount onto the tripod mount
platform, then b) secure it from the underside with azimuth lock knob.
Azimuth
lock knob
Washer
Figure 8.Screw in the latitude adjustment bolt.
Figure 9.Thread the counter-
weight shaft into the declination
housing.
Figure 10.The
counterweight, installed.
Lock knob
Latitude adjustment
bolt

7
2. Loosen the counterweight lock knob and slide the counter-
weight along the shaft until the telescope remains in any
given position without tending to drift up or down relative
to the polar axis (Figure 19). Then retighten the counter-
weight lock knob, locking the counterweight in that posi-
tion. If you can’t tell where the balance point is, just set the
counterweight halfway up the counterweight shaft and lock
it there.
The telescope is now balanced.
4. Understanding and Using
the Equartorial Mount
When you look at the night sky, you no doubt have noticed
the stars appear to move slowly from east to west over time.
That apparent motion is caused by the Earth’s rotation (from
west to east). An equatorial mount 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 eld of view while you’re observing.
An equatorial mount has two perpendicular axes: right ascen-
sion and declination (Figure 18).The R.A. axis, also known as
the “polar” axis, can be aligned to be parallel with the Earth’s
axis of rotation, thus allowing easy tracking of the night sky.
This is accomplished by slowly rotating the telescope on its
R.A. axis. The process of aligning the mount’s R.A. axis with
the Earth’s rotational (polar) axis is called polar alignment.
Polar Alignment
For Northern Hemisphere observers, approximate polar align-
ment is achieved by pointing the mount’s right ascension axis
at the North Star (Polaris). It lies within 1° of the north celes-
tial pole (NCP), which is an extension of the Earth’s rotational
axis out into space. Stars in the Northern Hemisphere appear
to revolve around the NCP.
To nd Polaris in the sky, look north and locate the pattern of the
Big Dipper (Figure 20). 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).
To polar align the Observer 80ST’s equatorial mount:
1. Roughly level the equatorial mount by adjusting the length
of the three tripod legs as needed.
2. Loosen the latitude lock knob (see Figure 11). Turn the lat-
itude adjustment bolt until the pointer on the latitude scale
is indicating the latitude of your observing location (Figure
18). If you don’t know your latitude, you can look it up on
the internet. For example, if your latitude is 35° North, set
the pointer to 35. Then retighten the latitude lock knob.
The latitude setting should not have to be adjusted again
unless you move to a different viewing location some dis-
tance away.
3. Loosen the Dec. lock knob and rotate the telescope optical
tube until it is parallel with the R.A. axis, as it is in Figure
2. The pointer on the Dec. setting circle should read 90°.
Retighten the Dec. lock knob.
4. Loosen the azimuth lock knob at the base of the equatorial
mount (Figure 18) and rotate the mount so the R.A. axis
points roughly at Polaris. If you cannot see Polaris directly
from your observing site, consult a compass and rotate the
mount so the telescope points North. Retighten the azi-
muth lock knob.
The equatorial mount is now polar aligned. From this point
on in your observing session, you should not make any
further adjustments to 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.
Figure 11. Rear view of the equatorial mount, with the two slow-
motion cables attached.
Figure 12. Line up the slow-motion cable thumbscrew with the
groove in the gear shaft, then tighten.
R.A. slow-
motion cable
Slow-motion
cable
Dec. slow-
motion cable
Latitude lock
knob
Thumbscrew
Latitude adjustment
bolt
Gear shaft
Groove

8
Using the R.A. and Dec. Slow-Motion Control
Cables
The R.A. and Dec. slow-motion control cables allow fine
adjustment of the telescope’s position to center objects with-
in the eld of view. Before using the cables, manually “slew”
the mount to point the telescope in the vicinity of the desired
target. Do this by loosening the R.A. and Dec. lock knobs
(Figure 18) and moving the telescope about the mount’s R.A.
and Dec. axes. Once the telescope is pointed somewhere
close to the object to be viewed, retighten the mount’s R.A.
and Dec. lock knobs.
The object should now be visible somewhere in the eld of
view of the red dot nder scope. If it isn’t, use the slow-motion
controls to scan the surrounding area of sky. Note: when
using the slow motion cables, the R.A. and Dec lock
knobs should be tightened, not loose. When the object
is visible in the nder scope, use the slow-motion controls to
Figure 13.The fully assembled equatorial mount.
Figure 14.Attach the optical tube to the mount’s saddle plate with
the supplied wingnuts and washers.
Wing nut
Saddle
Washer
Washer
Figure 15.Insert the red dot nder scope’s bracket into the base
near the focuser as shown.
Bracket
foot
Finder Scope
Base
Figure 16.Secure the star diagonal in the focuser drawtube with
the two thumbscrews, then secure the eyepiece in the diagonal.
Diagonal
Eyepiece
Focus
drawtube
Focus
wheels
Figure 17. The red dot nder scope has vertical and (inset)
horizontal adjustment knobs for aligning it with the telescope.
Power switch
Plastic
tab
Vertical knob
Horizontal knob
Opposite side

9
center the red dot on it. Now, look in the telescope’s eyepiece
and use the slow-motion controls to center it in the eyepiece.
The Dec. slow-motion control cable can move the telescope a
maximum of 25° or so. This is because the Dec. slow-motion
mechanism has a limited range of mechanical travel. (The R.A.
slow-motion mechanism has no limit to its amount of travel.)
If you can no longer rotate the Dec. control cable in a desired
direction, you have reached the end of travel, and the slow-
motion mechanism must be reset. This is done by rst rotating
the control cable several turns in the opposite direction from
which it was being turned. Then, manually slew the telescope
closer to the object you wish to observe (remember to rst
loosen the Dec. lock knob). You should now be able to use the
Dec. slow-motion control cable again to ne adjust the tele-
scope’s position.
Tracking Celestial Objects
When you observe a celestial object through the telescope,
you’ll see it drift slowly across the eld of view. To keep it in the
eld, assuming your equatorial mount is polar aligned, just turn
the R.A. slow-motion control cable clockwise, if the slow-motion
cable is mounted on the EAST side of the mount. If it’s on the
WEST side of the mount, turn it counterclockwise to track. The
Dec. slow-motion control cable is not needed for tracking. Objects
will appear to move faster at higher magnications, because the
eld of view is narrower.
Optional Electronic Drives for Automatic Tracking
An optional DC electronic drive can be mounted on the R.A. axis
of the equatorial mount to provide hands-free tracking. Objects
will then remain stationary in the eld of view without any manual
adjustment of the R.A. slow-motion control cable.
Understanding the Setting Circles
The two setting circles (Figure 18) on an equatorial mount
enable you to locate celestial objects by their “celestial coordi-
nates”. Every object resides in a specic location on the “celestial
sphere”. That location is denoted by two numbers: its right ascen-
sion (R.A.) and declination (Dec.). In the same way, every loca-
tion 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 mount’s R.A. setting circle is scaled in hours, from 1 through
24, with small marks in between representing 10-minute incre-
ments. The numbers closest to the R.A. axis gear apply to view-
ing in the Southern Hemisphere, while the numbers above them
apply to viewing in the Northern Hemisphere.
Figure 18. Components of the equatorial mount, seen from both sides.
R.A. Slow-motion cable
Dec. Slow-
motion
cable
Dec. Slow-
motion
cable
Dec. lock
knob
Dec. Setting circle
R.A.
Setting
circle
R.A. Setting
circle
R.A. lock
knob
Latitude
scale
Latitude
lock knob
Latitude
adjustment
bolt
Azimuth
lock knob
Declination (Dec.) axis
Declination (Dec.) axis
Figure 19. Balance the telescope on the R.A. axis by positioning
it as shown and sliding the counterweight until balance is achieved.
R.A. lock knob

10
The Dec. setting circle is scaled in degrees, with each mark rep-
resenting 2.5° increments.Values of Dec. coordinates range from
+90° to -90°. The 0° mark indicates the celestial equator. When
the telescope is pointed north of the celestial equator, values of
the Dec. setting circle are positive, while when the telescope is
pointed south of the celestial equator, values of the Dec. setting
circle are negative.
So, the coordinates for the Orion Nebula are:
R.A. 5h 35.4m Dec. -5° 27’
That’s 5 hours and 35.4 minutes in right ascension, and -5
degrees and 27 arc-minutes in declination (there are 60 arc-min-
utes in 1 degree of declination).
Before you can use the setting circles to locate objects, the
mount must be properly polar aligned, and the R.A. setting circle
must be calibrated. The Dec. setting circle has been permanently
calibrated at the factory, and should read 90° whenever the tele-
scope optical tube is parallel with the R.A. axis.
Calibrating the Right Ascension Setting Circle
1. Identify a bright star in the sky near the celestial equator
(Dec. = 0°) and look up its coordinates in a star atlas.
2. Loosen the R.A. and Dec. lock knobs on the equatorial
mount, so the telescope optical tube can move freely.
3. Point the telescope at the bright star whose coordinates
you know. Lock the R.A. and Dec. lock knobs. Center the
star in the telescope’s eld of view with the slow-motion
control cables.
4. Rotate the setting circle until the metal arrow indicates the
R.A. coordinate listed in the star atlas for the object.
Finding Objects with the Setting Circles
1. Now that both setting circles are calibrated, look up in a
star atlas the coordinates of an object you wish to view.
2. Loosen the R.A. lock knob and rotate the telescope until
the R.A. value from the star atlas matches the reading on
the R.A. setting circle. Remember to use the upper set
of numbers on the R.A. setting circle. Retighten the lock
knob.
3. Loosen the Dec. lock knob and rotate the telescope until
the Dec. value from the star atlas matches the reading on
the Dec. setting circle. Remember that values of the Dec.
setting circle are positive when the telescope is pointing
north of the celestial equator (Dec. = 0°), and negative
when the telescope is pointing south of the celestial equa-
tor. Retighten the lock knob.
Most setting circles are not accurate enough to put an object
dead-center in the telescope’s eyepiece, but they should place
the object somewhere within the eld of view of the red dot
nder scope, assuming the equatorial mount is accurately polar
aligned. Use the slow-motion controls to center the object in the
nder scope, and it should appear in the telescope’s eld of view.
The R.A. setting circle must be re-calibrated every time you wish
to locate a new object. Do so by calibrating the setting circle for
the centered object before moving on to the next one.
Confused About Pointing the Telescope?
Beginners occasionally experience some confusion about how
to point the telescope overhead or in other directions. One thing
you DO NOT do is make any adjustment to the mount’s latitude
setting or to its azimuth position (don’t touch the azimuth lock
knob). That will throw off the mount’s polar alignment. Once the
mount is polar aligned, the telescope should be moved only
about the R.A. and Dec. axes by loosening one or both of the
R.A. and Dec. lock knobs and moving the telescope by hand, or
keeping the knobs tightened and moving the telescope using the
slow-motion cables.
5. Astronomical Observing
For many, this will be your rst foray into the exciting world of
amateur astronomy. The following information and observing
tips will help get you started.
Choosing an Observing Site
When selecting a location for observing, get as far away as pos-
sible from direct articial light such as street lights, porch lights,
and automobile headlights. The glare from these lights will great-
Big Dipper
(in Ursa Major)
Little Dipper
(in Ursa Minor)
Cassiopeia
N.C.P.
Pointer
Stars
Polaris
Figure 20. To nd Polaris in the night sky, look north and nd the
Big Dipper. Extend an imaginary line from the two "Pointer Stars"
in the bowl of the Big Dipper. Go about ve times the distance
between those stars and you'll reach Polaris, which lies within 1° of
the north celestial pole (NCP).
Figure 21. The Kellner eyepieces have barrels threaded to
accept optional Orion 1.25" lters. A Moon lter is useful for cutting
glare and revealing more detail on the lunar surface.