ORION TELESCOPES & BINOCULARS SkyLine 52136 User manual

IN 615 Rev. A 04/18
Optronic SkyLine™6"
Dobsonian Reflector
#52136
INSTRUCTION MANUAL
Copyright © 2018 Optronic Technologies
All Rights Reserved. No part of this product instruction or any of its contents may be reproduced,
copied, modified or adapted, without the prior written consent of Optronic Technologies.

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Contents
1................................... Included Parts
2 ......................................Assembly
3............................. Using Your Telescope
4......................................Collimation
5....................................Specifications
1. Included Parts
Your SkyLine 6"Dobsonian comes packaged in two shipping
boxes. Refer to Figures 2 and 3 to make sure all the parts
shown are present.
2. Assembly
Assembly of the Base
The base needs to be assembled only once. The assembly
takes about 20 minutes and requires a Phillips screwdriver and
the two included Allen wrenches (small and large). Refer to
Figure 2 for identification of the base parts.
NOTE: When tightening the base assembly screws, tight-
en them until firm, but be careful not to strip the holes by
over-tightening. If you use an electric screwdriver, do the
WARNING: NEVER look directly at the Sun
through your telescope—even for an instant—
without a professionally made solar filter that
completely covers the front of the instrument,
or permanent eye damage could result. Young
children should use this telescope only with
adult supervision.
Optronic SkyLine Dobsonians are big, fun telescopes with exceptional features and accessories that
give them a performance edge. This instruction manual will guide you through the one-time assembly
process for the SkyLine 6"Dobsonian and provide other important information about your new tele-
scope. Read it over carefully and if you still have questions, call Orion Customer Service at 800-676-
1343 or send an email to [email protected].
Figure 1. The SkyLine 6"Dobsonian Figure 2. a) Base board components of the SkyLine 6"Dobsonian.
b) Base assembly hardware.
Eyepiece
Focuser
Finder scope
Side panels Ground plates
Front panel
Optical tube
Eyepiece
Side bearing
Spring
tensioner
Eyepiece
rack
Handle
Base
2b
Base assembly
screws Feet Azimuth
tension bolt
Washer
Ball bearing
ring
Allen
wrenches
Spring
tensioners
Large
washer
Handle
Handle
mounting
screws
Pull rings
Washers
Machine
Screws
Spacer
posts
Wood
screws
Bolts with
round knob
Azimuth axle
sleeve
2a

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final tightening with a standard screwdriver to avoid strip-
ping.
1. Find the ground plate with the threaded metal insert in the
center hole. On one side the metal insert is nearly flush
with the goundplate surface – this is the bottom side of the
groundplate (Figure 4). Screw the 3 plastic feet into the
small holes on this side using the long Philips-head wood
screws provided, with a Phillips screwdriver (Figure 5).
2. Attach the front panel to the two side panels with four black
base assembly screws in the predrilled holes (Figure
6a). Use the included small Allen wrench to tighten the
screws. Orient the front panel so that the metal T-nuts
face inward. The side panel with the two predrilled holes
for the eyepiece rack should be installed on the LEFT side
(Figure 6b).
3. Now stand the panel assembly upside down, exposing the
bottom edge of the panels. Lay the top goundplate on the
panel assembly, aligning the holes in the groundplate with
those in the panel edges (Figure 7). NOTE: Make sure
the countersunk holes in the ground plate are facing
UP.
4. Attach the goundplate to the panel assembly with four
base assembly screws in the predrilled holes, using the
small Allen wrench. Tighten all screws.
5. Install the eyepiece rack with the two small wood screws
provided in the predrilled holes on the left side panel.
You will need a Philips screwdriver to tighten the screws
(Figure 8).
Optical tube
Collimation
cap
Dust cover 25mm
Plössl 9mm
Plössl Finder scope
bracket
Rubber
o-ring
Eyepiece rack
Rack mounting
screws
6x30 finder
scope
Figure 3. Optical tube assembly and accessories.
Figure 5. Install the three
feet with the included screws on
the bottom side of the bottom
groundplate.
Figure 6. a) Attach the two side panels to the front panel with the
base assembly screws and included Allen wrench. b) The side panel
with the two holes for the eyepiece rack should go on the left side.
Left
side
panel
Right
side
panel
Front panel
Figure 4. The non-threaded
end of the metal insert is nearly
flush with the bottom side of the
bottom groundplate.
a b

4
6. Install the base handle on the front panel using the two
handle mounting screws and the small Allen wrench..
Insert the screws through the holes in the handle and into
the holes containing metal threaded inserts in the front
panel, then tighten (Figure 9).
7. Attach a nylon spacer post to both side panels using a
black Philips-head machine screw and 1/4"black washer
as indicated in Figure 10.
8. Now place the metal azimuth axle sleeve in the center hole
of the bottom groundplate, as in Figure 11.
9. Pick up the top base assembly and place it on the bottom
groundplate assembly, lining up the center hole in the top
ground-plate with the axle sleeve. The top base assembly
should now freely rotate on the bottom groundplate.
10.On the azimuth tension bolt (with rosette knob), place the
small silver washer, the ball bearing ring, and the large
washer, in that order (Figure 12a). Then thread the bolt
into the center hole of the top groundplate and rotate the
knob until the desired tension is achieved (12b).
Your Dobsonian base is now fully assembled and should
appear as in Figure 13.
Figure 7. With the front and side panel assembly turned
upside down, attach the top groundplate to the assembly with the
countersunk holes facing up.
Top groundplate
Countersunk hole
Figure 8. Install the eyepiece rack on the left side panel with the
two small wood screws provided.
Figure 9. Use the Allen
wrench and the two included
handle mounting screws to
attach the handle to the front
panel
Figure 10. Attach a plastic
spacer on each side panel using a
black washer and machine screw
as indicated. The thicker end of
the spacer should be closest to the
side panel.
Figure 11. With the bottom groundplate standing on its three feet,
insert the azimuth axle sleeve into the center hole of the groundplate.
Washer
Spacer
Post

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Installing the Optical Tube Assembly on the Base
1. Put one of the black plastic spacer posts on a bolt with
round knob. The spacer post should be oriented so the
narrow end is closest to the round knob.
2. Place one end loop of a spring tensioner onto the bolt, over
the spacer.
3. Then thread the bolt into the hole in the optical tube’s
altitude side bearing and tighten (Figure 14).
4. Place a pull ring onto the free end loop of the spring
(Figure 15).
5. Repeat steps 1 to 4 on the other side of the tube.
6. Now lift the optical tube and place it onto the base,
lowering the side bearings into the cradle wells at the top
of the side panels (Figure 16). The side bearings will rest
on the white Teflon pads in the wells. The tube should be
oriented so that the focuser faces the left side of the base
(the side with the eyepiece rack), as in the picture.
7. Now, on one side, pull the spring tensioner downward
using the pull ring, and position the spring’s end loop –
NOT the pull ring itself – over the head of the Phillips screw
and onto the narrow part of the nylon spacer, as shown in
Figure 17. Then do the same for the other side of the
telescope.
If you wish to remove the telescope from the base, you will first
need to disconnect the springs from the spacer posts on the
Dobsonian base. The springs will remain captive on the optical
tube’saltitudesidebearings,sotheywillnotgetlost.
To Install the Finderscope
The SkyLine 6"Dobsonian comes with a 6x30 achromatic
crosshair finder scope as standard equipment. Its wide field of
view greatly aids in finding and centering objects for viewing in
the main telescope.
1. To do so, first remove the rubber O-ring from the bracket.
Now insert the foot of the finder scope bracket into the
dovetail holder near the focuser (Figure 18). Lock the
bracket into position by tightening the knurled thumb screw
on the dovetail holder.
2. Now place the O-ring onto the finder scope tube until it
seats in the groove in the tube (Figure 19).
Figure 12. a) Place the two washers and roller bearing ring on
the azimuth tension bolt as shown. b) Then thread the bolt into the
center hole (metal insert) and tighten to the desired tension.
b)
Small washer
Ball bearing
Large washer
Figure 13. The assembled Dobsonian base.
a b
Figure 14. Place a spring
tensioner and plastic spacer on a
bolt with round knob as shown,
then thread the bolt into the
center hole of the side bearing on
the optical tube until tight. Repeat
on the other side.
Figure 15. Place a pull ring
on the free end of each spring
tensioner.
Pull ring

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3. Then unthread the two screws on the bracket until the
screw ends are flush with the inside diameter of the
bracket. While pulling the spring pin, slide the eyepiece
end (narrow end) of the finder scope into the end of the
bracket’scylinderoppositethealignmentscrews(Figure
19). Push the finder scope through the bracket until the
O-ringseatsjustinside thefrontopeningofthebracket’s
cylinder. Now, release the tensioner and tighten the two
thumbscrews a couple of turns each to secure the finder
scope tube in the bracket.
Installing an Eyepiece
Your SkyLine 6"Dobsonian comes with two Plossl type eye-
pieces equipped with a 1.25"-diameter chrome barrel: one has
a 25mm focal length and the other a 9mm focal length. To install
an eyepiece in the focuser, first remove the cap from the fo-
cuser, then insert the chrome barrel of the eyepiece into the
drawtube collar (Figure 20). Secure the eyepiece with the
thumbscrew on the collar. You can keep the other eyepiece in
theeyepiecerackonthebaseuntilyou’rereadytouseit.
Your SkyLine 6"Dobsonian is now fully assembled! The dust
cover on the front of the telescope should always remain in
place when the telescope is not in use. It is also a good idea to
store eyepieces in an eyepiece case and to replace the cover
cap on the focuser when the telescope is idle.
3. Using Your Telescope
It is best to get a feel for the basic functions of the SkyLine
Dobsonian during the day, before observing astronomical
objects at night. This way you will not have to fumble around
trying to orient yourself in the dark! Find a spot outdoors where
you have plenty of room to move around the telescope, and
where you have a clear view of some object or vista that is at
least 1/4-mile away. It is not critical that the base be exactly
level, but it should be placed on somewhat flat ground to ensure
smooth movement of the telescope.
Altitude and Azimuth
The Dobsonian base permits motion of the telescope along two
axes: altitude (up/down) and azimuth (left/right) (Figure 21).
As a result, pointing the telescope is exceptionally easy. Simply
take hold of the end of the tube and move it left or right so the
Figure 18. Slide the foot of
the finder scope bracket into the
dovetail base as shown, and lock
it with the thumbscrew.
Figure 19. With the rubber
O-ring seated in the groove,
insert the finder scope into the
bracket as shown until the O-ring
seats under the bracket cylinder.
You will need to pull back on the
spring pin while doing this.
Dovetail
holder
Thumbscrew
O-ring
Spring
pin
Lock ring
Objective lens
cell
Figure 16. Lift the optical tube and place it in the base as shown.
Figure 17. Using the pull ring (a), pull the spring tensioner over
the screw head of the spacer post on the side panel to secure the
optical tube on the base (b).
a b

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base rotates about its central azimuth bolt, and move it up or
downsothealtitudesidebearingsrotateinthebase’scradle.
Both motions can be made simultaneously and in a continuous
manner for easy aiming. In this way you can point the telescope
to any position in the night sky, from horizon to horizon.
The azimuth motion should be smooth, with just enough resis-
tance to keep the base from rotating when you want it to stop
and stay put after you have slewed the telescope. Azimuth ten-
sion, or friction, can be adjusted with the azimuth tension knob
in the center of the top groundplate – turn it clockwise for more
tension, counterclockwise for less.
The tension for the altitude motion is not adjustable; the spring
tensioners are designed to apply an appropriate amount of
constant tension to achieve smooth up and down motion while
keeping the optical tube from drifting when you let go of it.
Focusing the Telescope
With the 25mm eyepiece secured in the focuser, move the tele-
scope so the front (open) end is pointing in the general direction
of an object at least 1/4-mile away. Now, with your fingers, slow-
ly rotate one of the focusing knobs until the object comes into
sharp focus. Go a little bit beyond sharp focus until the image
just starts to blur again, then reverse the rotation of the knob,
justtomakesureyou’vehittheexactfocuspoint.
If you have trouble focusing, rotate the focusing knob so the
drawtube is in as far as it will go. Now look through the eyepiece
while slowly rotating the focusing knob in the opposite direction.
You should soon see the point at which focus is reached.
The Crayford type focuser of the SkyLine 6"Dobsonian features
two thumbscrews on the bottom of the focuser body (Figure
20), which allow adjustment of the drawtube tension and will
lock the focuser drawtube in place once the telescope is prop-
erly focused, if desired.
If you find the drawtube tension when focusing is either too tight
(drawtubedoesn’tmovewhenyouturnthefocusknobs)ortoo
loose (drawtube slips under the weight of the eyepiece), the
tension can be adjusted for optimal performance.
Aligning the Finder Scope
The finder scope must be aligned accurately with the optical
tube of the telescope for proper use. This way, when you center
an object in the finder scope, it will also be centered in the main
telescope’seyepieceandreadyto view.Thefinder scope’s
bracket has two perpendicular alignment thumbscrews and a
silver spring pin. To align the finder scope you will adjust the
two thumbscrews, which alters the direction the finder scope is
pointing.
First aim the main telescope in the general direction of an object
at least 1/4-mile away, e.g., the top of a telephone pole, a chim-
ney,etc.Positionthatobjectinthecenterofthetelescope’s
eyepiece.
NOTE: The image in the main telescope will appear upside-
down (rotated 180°). This is normal for reflector telescopes.
Now look through the finder scope. Ideally, the object should be
visible in the field of view. If it is not, then coarse adjustments to
thefinderscopebracket’salignmentthumbscrewswillbeneed-
ed.Oncetheimageisinthefinderscope’sfieldofview,youwill
now use the alignment thumbscrews to center the object on the
intersection of the crosshairs. By loosening or tightening one
or both alignment thumbscrews, you change the line of sight of
the finder scope. Continue making adjustments to the alignment
thumbscrews until the image in both the finder scope and the
telescope’seyepieceareexactlycentered.
Check the alignment by moving the telescope to another object
andfixingthefinderscope’scrosshairsontheexactpointyou
wanttolookat.Thenlookthroughthetelescope’seyepieceto
Figure 21. The SkyLine 6"Dobsonian has two axes of motion:
altitude (up and down) and azimuth (left and right).
Figure 20. Insert the eyepiece barrel into the focuser and secure it
with the thumbscrew.
Thumbscrew
lock
Focus wheel
Drawtube
tensioning
thumbscrews
Altitude
Azimuth

8
see if that point is centered in the field of view. If it is, the job
is done. If not, make the necessary adjustments until the two
images match up.
The finder scope alignment should be checked before every
observing session.
Magnification
Magnification, or power, is determined by the focal length of the
telescope and the focal length of the eyepiece. Magnification is
calculated as follows:
Magnification of the telescope can be changed by using differ-
ent eyepieces. For example, the SkyLine 6"Dobsonian has a
focal length of 1200mm. So, the magnification with the supplied
9mm Plossl eyepiece is:
By the same formula, when using the 25mm Plossl eyepiece,
the magnification would be 48x.
The maximum attainable magnification for a telescope is direct-
ly related to how much light its optics can collect. A telescope
with more light-collecting area, or aperture, can yield higher
magnifications than a smaller aperture telescope. The maxi-
mum practical magnification for any telescope, regardless of
optical design, is about 50x per inch of aperture. This translates
to about 300x for the SkyLine 6".
Keep in mind that as magnification is increased, the brightness
of the object being viewed will decrease; this is an inherent prin-
ciple of the physics of optics and cannot be avoided. If mag-
nification is doubled, an image appears four times dimmer. If
magnification is tripled, image brightness is reduced by a factor
of nine!
Maximum magnifications are achieved only under the most
ideal viewing conditions at the best observing sites. Most of the
time, magnification is limited to 200x or less, regardless of aper-
ture.ThisisbecausetheEarth’satmospheredistortslightasit
passes through. On nights of good “seeing,” the atmosphere
will be still and will yield the least amount of distortion. On nights
of poor seeing, the atmosphere will be turbulent, which means
different densities of air are rapidly mixing. This causes signifi-
cant distortion of the incoming light, which prevents sharp views
at high magnifications. The sharpest images will always be
achieved at lower magnifications.
Cooling the Optics
All optical instruments need time to reach “thermal equilibrium”
with the ambient air to achieve maximum stability of the lenses
and mirrors, which is essential for peak performance. When
moved from a warm indoor location to cooler air outside (or
vice-versa), a telescope needs time to equilibrate to the outdoor
temperature. The bigger the instrument and the larger the tem-
perature change, the more time will be needed.
Allow at least 30 minutes for your SkyLine Dobsonian to equili-
brate. If the scope experiences more than a 40° temperature
change, allow an hour or more. In the winter, storing the tele-
scope in a shed or garage greatly reduces the amount of time
needed for the optics to stabilize. It also is a good idea to keep
the scope covered until the Sun sets so the tube does not heat
greatly above the temperature of the outside air.
Carrying/Transporting the Telescope
Moving the SkyLine Dobsonian is easy to do. Because the
spring tensioners hold the optical tube captive on the base, the
entire telescope can be carried as one unit. This requires some
caution, however. If the telescope is lifted improperly, the front
of the tube could swing down and hit the ground. First, point the
optical tube straight up (vertical). Remove any eyepieces from
the telescope and optional eyepiece rack, and place them in an
eyepiece case. Grasp the handle on the front of the base with
one hand while supporting the telescope tube vertically with the
other. Now, lift the telescope from the handle. Once the tele-
scope is in the horizontal position, you can carry the entire unit
with one hand. If you wish to carry the optical tube and base
separately, simply disengage the springs by unhooking them
from the posts on the base, using the pull rings. The springs
remain captive on the telescope side bearings. Now the base
and tube are disengaged and can be transported separately.
When putting the telescope into a vehicle, common sense pre-
vails. It is especially important that the optical tube does not
knock around; this can cause the optics to become misaligned,
and could dent the tube. We recommend transporting and stor-
ing the tube assembly in a padded case for proper protection.
Finally, keep the dust cover on the front of the telescope when it
is not in use. Doing so will keep dust from accumulating on the
primary mirror.
4. Collimation
Collimation is the process of adjusting the mirrors so they are
correctlyalignedwithoneanother.Yourtelescope’sopticswere
aligned at the factory, but they could have become misaligned
during shipment. Accurate mirror alignment is important to
ensure the peak performance of your telescope, so it should be
checked regularly. Collimation is relatively easy to do and can
be done in daylight or in the field at night.
The Collimation Cap
Your Orion SkyLine 6"Dobsonian comes with a “quick collima-
tion cap,” shown in Figure 22. This is a simple cap that fits
on the focuser drawtube like a dust cap, but has a tiny hole in
the center. The collimation cap helps center your eye over the
focuser drawtube, making it easier to align the optical compo-
nents.Thewhitesurfaceandblackringonthecap’sunderside
provide a distinct visual reference that is helpful in centering the
mirror reflections.
= Magnification
Telescope Focal Length (mm)
Eyepiece Focal Length (mm)
= 133x
1200 mm
9 mm

9
Primary Mirror Center Mark
The primary mirror of your telescope has a tiny ring (sticker)
marking its center. This “center mark” is helpful in achieving a
precise collimation. Do not remove it! Because it lies directly
in the shadow of the secondary mirror, its presence in no way
adversely affects the optical performance of the telescope or
theimagequality.Thatmightseemcounterintuitive,butit’strue!
Preparing the Telescope for Collimation
Once you get the hang of collimating, you will be able to do it
quickly even in the dark. For now, it is best to collimate in day-
light, preferably in a brightly lit room and aimed at a light colored
wall. It is recommended that the telescope tube be oriented hor-
izontally. This will prevent any parts from the secondary mirror
from falling down onto the primary mirror and causing damage
if something comes loose while you are making adjustments.
Place a small sheet of white paper inside the optical tube direct-
ly opposite the focuser (Figure 23). The paper will provide a
bright “background” when viewing into the focuser.
Aligning the Secondary Mirror
There are two adjustments to the secondary mirror that you
may have to make. The first is to center the secondary mirror in
the circle formed by the focuser drawtube. This adjustment will
rarely,ifever,needtobedone.Thesecondadjustmentyou’ll
make is to the tilt of the secondary mirror, to make sure all the
light from the primary mirror is properly reflected up through the
focuser into the eyepiece. This is the more common secondary
mirror adjustment.
To make adjustments to the secondary mirror tilt, you will need
a small Philips screwdriver. Remember to always slightly loosen
(by 1/4 turn or less) one screw before tightening one or both of
the other two screws. And do not overtighten them or you could
damage the secondary mirror support housing!
Centering the Secondary Mirror in the Focuser
Drawtube
Let’sstartwiththefirstadjustment–centeringthesecondary
mirror in (actually, under) the focuser drawtube. With the col-
limation cap in place on the focuser collar, look through the hole
in the collimation cap at the secondary (diagonal) mirror. Ignore
the reflections for the time being. The secondary mirror itself
should be centered in the circle of the focuser drawtube. If it
is, as in Figure 24c, you can move on to the next section,
AdjustingtheSecondaryMirror’sTilt.Ifitisn’tcentered,asin
Figure 24b, it must be adjusted as follows.
Using a Philips screwdriver, loosen the three small alignment
setscrews in the center hub of the 4-vaned spider several turns
(Figure 25a). Now hold the mirror holder stationary (be care-
ful not to touch the surface of the mirror), while turning the cen-
ter screw with a Phillips head screwdriver. Turning the screw
clockwise will move the secondary mirror toward the front open-
ing of the optical tube, while turning the screw counter-clock-
wise will move the secondary mirror toward the primary mirror.
When the secondary mirror is centered under the focuser draw-
tube, rotate the secondary mirror holder until the reflection of
the primary mirror is as centered in the secondary mirror as
possible. It may not be perfectly centered, but that is OK. Now
tighten the three small alignment screws equally to secure the
secondary mirror in that position. If the entire primary mirror
reflection is not visible in the secondary mirror, as in Figure
24c, you will need to adjust the tilt of the secondary mirror.
Adjusting the Secondary Mirror’s Tilt
The goal with this adjustment is to center the primary mirror
reflection in the secondary mirror, as in Figure 24d.Don’t
worry that the reflection of the secondary mirror (the smallest
circle, with the collimation cap “dot” in the center) is off-center.
You will fix that in the next step. Using the Philips screwdriver,
first loosen one of the three alignment screws by no more than
¼ turn, then lightly tighten the other two to take up the slack. Is
the primary mirror reflection more centered now? If not, then
try loosening one of the other two screws. Always loosen one
first, then tighten one or both of the other two screws. It will take
some trial and error, but by adjusting the three small screws a
small amount at a time, you should be able eventually to see the
whole primary mirror in the secondary mirror, just like in Figure
Figure 22. The quick
collimation cap assists in
ensuring precise optical
alignment.
Figure 23. The SkyLine 6"Dobsonian ready for collimation.
Orient the tube horizontally and place a piece of white paper
inside the tube opposite the focuser.

10
24d. At the end of the procedure all three alignment screws
shouldbetight–butdon’tovertighten!--toensurethatthesec-
ondarymirrorcan’tmove.
Aligning the Primary Mirror
The final adjustment is made to the primary mirror. It will need
adjustment if, as in Figure 24d, the secondary mirror is cen-
tered under the focuser and the reflection of the primary mirror
is centered in the secondary mirror, but the small reflection of
the secondary mirror (with the “dot” of the collimation cap) is
off-center. The tilt of the primary mirror is adjusted with three
spring-loaded collimation thumb-screws on the bottom end of
the optical tube (Figure 25b); these are the larger thumb-
screws.Theotherthree,smallerthumbscrewslockthemirror’s
position in place; these locking thumbscrews must first be loos-
ened before any collimation adjustments can be made to the
primary mirror.
To start, loosen the locking thumbscrews a few turns each.
Now, try tightening or loosening one of the larger collimation
thumbscrews with your fingers. Look into the focuser and see if
the secondary mirror reflection has moved closer to the center
of the primary. You can tell this easily with the collimation cap
and mirror center mark by simply watching to see if the “dot”
of the collimation cap is moving closer or farther away from the
ring on the center of the primary mirror. If the dot moved far-
ther away from the ring, try turning the thumbscrew the opposite
way, or try turning a different collimation thumbscrew and see-
ing what happens. When you have the dot centered as much
as possible in the ring, your primary mirror is collimated. The
view through the collimation cap should now resemble Fig-
ure 24e. Retighten the locking thumbscrews. The true test of
whetheryourtelescope’sopticsareaccuratelycollimatedisa
startest.Here’showtodoit.
Star-Testing the Telescope
To determine whether your optics are well collimated, when it is
dark, point the telescope at a bright star -- Polaris is ideal since
it will not drift noticeably -- and accurately center it in the eye-
piece’sfieldofview.Slowlyde-focustheimagewiththefocusing
knob. If the telescope is correctly collimated, the expanding disk
should be a perfect circle (Figure 26). If the image is unsym-
metrical, the scope is out of collimation. The dark shadow cast
by the secondary mirror should appear in the very center of the
out-of-focus circle, like the hole in a donut. If the “hole” appears
off-center, the telescope is out of collimation.
If you try the star test and the bright star you have selected is
not accurately centered in the eyepiece, the optics will always
appear out of collimation, even though they may be perfectly
aligned. It is critical to keep the star centered, so over time you
willneedtomakeslightcorrectionstothetelescope’spositionin
ordertoaccountforthesky’sapparentmotion.
c
Figure 24. Collimating the optics. (a) When the mirrors are
properly aligned, the view down the focuser drawtube should look
like this; (b) With the collimation cap in place, if the optics are out
of alignment, the view might look something like this; (c) Here, the
secondary mirror is centered under the focuser, but it needs to be
adjusted (tilted) so that the entire primary mirror is visible; (d) The
secondary mirror is correctly aligned, but the primary mirror still
needs adjustment. When the primary mirror is correctly aligned, the
“dot” will be centered, as in (e).
a
b
ed

11
5. Specifications
Objective lens: 1200mm
Primary mirror diameter: 152mm
Focal ratio: f/7.9
Minor axis of
secondary mirror: 33mm
Optics: Parabolic, diffraction limited
Mirror coatings: Enhanced aluminum (94%-96%
reflectivity), with SiO2 overcoat
Focuser: 1.25" Crayford
Optical tube material: Rolled steel
Eyepieces: 9mm Plössl, 1.25".
25mm Plössl, 1.25"
Magnification with
supplied eyepieces: 133x (9mm Plossl)
48x (25mm Plössl)
Finder scope: 6x30 achromatic
Collimation: Quick collimation cap included
Optical tube weight: 12 lbs. 8 oz
Base weight: 29 lbs. 1 oz.
Tube length: 45.5"
Tube outer diameter: 10.25" (including side bearings)
Figure 26. A star test will determine if a telescope’s optics are
properly collimated. An unfocused view of a bright star through
the eyepiece should appear as illustrated on the right if the optics
are perfectly collimated. If the circle is unsymmetrical, as in the
illustration on the left, the scope needs collimation.
Figure 25. a) The tilt of the secondary mirror is adjusted with
the three Philips screws shown here. b) The primary mirror’s tilt is
adjusted with the three large thumbscrews on the rear cell. The three
narrow locking thumbscrews should be loosened a couple of turns
first, then retightened once the adjustment has been made.
Center
screw
Alignment
screws
Locking
thumbscrew
Collimation
thumbscrew
ab

12
Optronic Technologies
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